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MCAT Psychological Social Foundations Quiz

MCAT Psychological Social Foundations Quiz: 7a Brain Neurotransmitters Behavior

Practice 7a Brain Neurotransmitters Behavior in MCAT Psychological Social Foundations with focused quiz questions that help you check what you know, review explanations, and build confidence with test-style prompts.

Question 1 / 20

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In a pharmacology experiment, 26 participants received either a selective 555-HT2A\text{HT}_{2A}HT2A​ receptor agonist at a subhallucinogenic dose or placebo before completing a cognitive reappraisal task during fMRI. The agonist increased functional coupling between medial prefrontal cortex (mPFC) and amygdala during reappraisal trials and was associated with greater reduction in negative affect ratings. Which outcome is most consistent with the observed neurotransmitter effects?

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What this quiz covers

This quiz focuses on 7a Brain Neurotransmitters Behavior, giving you a quick way to practice the rules, question types, and explanations that matter most for MCAT Psychological Social Foundations.

How to use this quiz

Try each quiz question before looking at the correct answer. Use the explanations to review missed ideas, then come back to similar questions until the pattern feels familiar.

All questions

Question 1

In a pharmacology experiment, 26 participants received either a selective 555-HT2A\text{HT}_{2A}HT2A​ receptor agonist at a subhallucinogenic dose or placebo before completing a cognitive reappraisal task during fMRI. The agonist increased functional coupling between medial prefrontal cortex (mPFC) and amygdala during reappraisal trials and was associated with greater reduction in negative affect ratings. Which outcome is most consistent with the observed neurotransmitter effects?

  1. Reduced reappraisal efficacy because serotonergic signaling prevents prefrontal regulation of amygdala activity
  2. Enhanced emotion regulation consistent with increased mPFC–amygdala coordination under serotonergic modulation (correct answer)
  3. Enhanced regulation driven by increased acetylcholine release in the spinal cord
  4. No effect on affect ratings because 555-HT2A\text{HT}_{2A}HT2A​ receptors are limited to the cerebellum

Explanation: This question tests the understanding of the interaction between brain structures, neurotransmitters, and behavior. Neurotransmitters influence behavior by affecting brain structures, which mediate responses. In this vignette, serotonin affects emotion regulation through the medial prefrontal cortex (mPFC) and amygdala. Choice B is correct because it accurately reflects the role of serotonergic modulation in enhancing mPFC-amygdala coordination. Choice A is incorrect because it misinterprets serotonergic signaling as preventing regulation, contrary to the observed improvements. When analyzing neurotransmitter effects, consider direct brain structure involvement and ensure conclusions align with observed data.

Question 2

In a study of memory consolidation, 27 participants received a β\betaβ-adrenergic antagonist before viewing emotionally negative and neutral images. Twenty-four hours later, recognition memory for negative images was selectively reduced in the drug group, while memory for neutral images was similar to placebo. Amygdala activation during encoding of negative images was reduced, but hippocampal activation during neutral encoding was unchanged. Which statement best explains the findings?

  1. Selective impairment indicates hippocampus is unnecessary for memory of emotional images
  2. Blocking norepinephrine increases amygdala activation, strengthening memory for negative images
  3. The effect is best explained by dopamine blockade in the cerebellum affecting neutral memory
  4. Blocking norepinephrine signaling reduces amygdala-related enhancement of emotional memory, selectively impairing consolidation of negative material (correct answer)

Explanation: This question tests the understanding of the interaction between brain structures, neurotransmitters, and behavior. Neurotransmitters influence behavior by affecting brain structures, which mediate responses. In this vignette, norepinephrine affects emotional memory through the amygdala. Choice D is correct because it accurately reflects the role of norepinephrine blockade in impairing consolidation of negative material. Choice B is incorrect because it misinterprets blockade as increasing activation, opposite to reduced memory effects. When analyzing neurotransmitter effects, consider direct brain structure involvement and ensure conclusions align with observed data. Consider valence-specific enhancements in memory encoding.

Question 3

Researchers administered a D2 receptor antagonist to 34 participants and then assessed effort-based decision making in a task requiring repeated choices between a low-effort/low-reward option and a high-effort/high-reward option. fMRI showed reduced nucleus accumbens activation during anticipation of high reward after drug administration, while amygdala activation to aversive images was unchanged. Participants chose the high-effort option less frequently. Which behavior change would be expected following neurotransmitter modulation?

  1. Greater selection of high-effort options due to increased dopaminergic tone in the nucleus accumbens
  2. Reduced willingness to expend effort for reward, consistent with decreased dopamine signaling in ventral striatum (correct answer)
  3. Enhanced fear conditioning due to increased dopamine release in the amygdala
  4. Improved declarative memory encoding due to D2 blockade in the hippocampus

Explanation: This question tests the understanding of the interaction between brain structures, neurotransmitters, and behavior. Neurotransmitters influence behavior by affecting brain structures, which mediate responses. In this vignette, dopamine affects effort-based decision making through the nucleus accumbens. Choice B is correct because it accurately reflects the role of decreased dopamine signaling in reducing motivation for high-effort rewards. Choice A is incorrect because it misinterprets the D2 antagonist as increasing dopaminergic tone, opposite to its blocking effect. When analyzing neurotransmitter effects, consider direct brain structure involvement and ensure conclusions align with observed data. Always verify how receptor modulation alters signaling pathways in reward-related behaviors.

Question 4

A study examined startle modulation in 24 participants after administration of a glycine receptor positive modulator. The drug increased inhibitory tone in brainstem circuits and reduced baseline startle magnitude to acoustic bursts. However, startle potentiation by conditioned threat cues (relative increase during threat vs safe) was unchanged, and amygdala activation to threat cues was similar across conditions. Which outcome is most consistent with the observed neurotransmitter effects?

  1. Reduced baseline startle with preserved threat potentiation, consistent with enhanced inhibition in brainstem reflex pathways without altering amygdala-driven modulation (correct answer)
  2. Increased baseline startle because glycine reduces inhibition in brainstem circuits
  3. Eliminated threat potentiation because glycine modulation primarily suppresses hippocampal memory encoding
  4. Reduced baseline startle due to increased dopamine release in nucleus accumbens

Explanation: This question tests the understanding of the interaction between brain structures, neurotransmitters, and behavior. Neurotransmitters influence behavior by affecting brain structures, which mediate responses. In this vignette, glycine affects startle reflexes through brainstem circuits. Choice A is correct because it accurately reflects the role of enhanced glycine inhibition in reducing baseline startle while preserving amygdala modulation. Choice B is incorrect because it misinterprets glycine as reducing inhibition, contrary to its inhibitory enhancement. When analyzing neurotransmitter effects, consider direct brain structure involvement and ensure conclusions align with observed data.

Question 5

In a rodent-inspired human analog task, 32 participants received a low-dose NMDA receptor antagonist before a contextual fear generalization test. fMRI showed reduced hippocampal pattern separation signals (lower differentiation between similar contexts) and increased generalization of fear ratings to safe contexts. Amygdala responses to the original threat context were unchanged. Which statement best explains the findings?

  1. Reduced glutamatergic NMDA signaling in hippocampus is consistent with poorer context discrimination and broader fear generalization (correct answer)
  2. NMDA antagonism increases hippocampal pattern separation, narrowing fear to the threat context
  3. Fear generalization is best explained by increased dopamine release in primary visual cortex
  4. Unchanged amygdala responses imply hippocampus is not involved in contextual aspects of fear learning

Explanation: This question tests the understanding of the interaction between brain structures, neurotransmitters, and behavior. Neurotransmitters influence behavior by affecting brain structures, which mediate responses. In this vignette, glutamate affects fear generalization through the hippocampus. Choice A is correct because it accurately reflects the role of reduced NMDA signaling in impairing context discrimination. Choice B is incorrect because it misinterprets NMDA antagonism as increasing pattern separation, contrary to the broader generalization observed. When analyzing neurotransmitter effects, consider direct brain structure involvement and ensure conclusions align with observed data. Assess how receptor blockade influences synaptic plasticity in memory systems.

Question 6

A lesion study compared 19 patients with focal damage to the basolateral amygdala (BLA) to 19 matched controls. During a fear-potentiated startle paradigm, patients showed reduced skin conductance responses to a conditioned stimulus and lower plasma epinephrine responses, while startle responses to loud noises without conditioning were preserved. The study also reported lower central release of corticotropin-releasing hormone but did not measure dopamine. Which statement best explains how the described brain structure influences behavior via neurotransmitter activity?

  1. BLA damage increases fear conditioning because epinephrine is the primary inhibitory neurotransmitter in cortex
  2. BLA damage selectively increases conditioned fear by enhancing serotonergic signaling in the hippocampus
  3. BLA damage impairs unconditioned startle reflexes by reducing acetylcholine release at neuromuscular junctions
  4. BLA damage disrupts associative threat learning, reducing downstream autonomic arousal that normally accompanies fear expression (correct answer)

Explanation: This question tests the understanding of the interaction between brain structures, neurotransmitters, and behavior. Neurotransmitters influence behavior by affecting brain structures, which mediate responses. In this vignette, epinephrine affects fear expression through the basolateral amygdala (BLA). Choice D is correct because it accurately reflects the role of BLA in associative learning and downstream autonomic arousal. Choice B is incorrect because it misinterprets BLA damage as increasing fear via serotonergic changes, opposite to the reduced responses observed. When analyzing neurotransmitter effects, consider direct brain structure involvement and ensure conclusions align with observed data. Evaluate how lesions disrupt specific pathways without affecting unrelated reflexes.

Question 7

A drug intervention study tested a nicotinic acetylcholine receptor (nAChR) agonist versus placebo in adults (n = 56) performing a sustained attention task with rare target stimuli. EEG-derived indices of attentional allocation were collected, and fMRI analyses focused on the thalamus and dorsolateral prefrontal cortex (DLPFC). Relative to placebo, the agonist increased target detection accuracy and was associated with increased thalamic activation during target presentation, with modest increases in DLPFC activation during sustained task periods. Which outcome is most consistent with the observed neurotransmitter effects and brain structure involvement?

  1. Lower target detection due to reduced thalamic sensory gating under increased cholinergic signaling
  2. Higher target detection consistent with enhanced cholinergic modulation of thalamic relay and frontoparietal attention networks (correct answer)
  3. Higher target detection driven primarily by decreased GABA activity in the cerebellum improving balance
  4. Lower target detection because acetylcholine acts only at neuromuscular junctions and not in the CNS

Explanation: This question tests the understanding of the interaction between brain structures, neurotransmitters, and behavior. Neurotransmitters influence behavior by affecting brain structures, which mediate responses. In this vignette, acetylcholine affects sustained attention through the thalamus and DLPFC. Choice B is correct because it accurately reflects the role of enhanced acetylcholine in modulating thalamic relay and attention networks, improving target detection. Choice A is incorrect because it misinterprets increased cholinergic signaling as reducing thalamic gating, which would not explain higher detection accuracy. When analyzing neurotransmitter effects, consider direct brain structure involvement and ensure conclusions align with observed data.

Question 8

Researchers tested whether enhancing serotonin (5-HT) signaling alters impulsive choice. Adults (n = 50) received either an acute selective serotonin reuptake inhibitor (SSRI) or placebo before performing a delay-discounting task (choices between smaller immediate rewards and larger delayed rewards). fMRI analyses focused on ventromedial prefrontal cortex (vmPFC) during valuation, and a peripheral biomarker index of central 5-HT tone was collected pre- and post-dose. Compared with placebo, the SSRI group showed higher 5-HT tone and increased vmPFC activation during evaluation of delayed rewards, along with fewer immediate-reward choices. Which behavior change would be expected following neurotransmitter modulation, most consistent with the described brain structure involvement?

  1. Greater preference for immediate rewards due to reduced vmPFC valuation of delayed outcomes under increased 5-HT tone
  2. More delayed-reward choices consistent with increased vmPFC engagement during future-oriented valuation under higher 5-HT tone (correct answer)
  3. No change in choice behavior because 5-HT affects only spinal reflexes rather than cortical valuation
  4. More immediate-reward choices due to increased norepinephrine signaling in the locus coeruleus driving arousal

Explanation: This question tests the understanding of the interaction between brain structures, neurotransmitters, and behavior. Neurotransmitters influence behavior by affecting brain structures, which mediate responses. In this vignette, serotonin affects impulsive choice through the vmPFC. Choice B is correct because it accurately reflects the role of increased serotonin in enhancing vmPFC valuation of delayed rewards, leading to more patient choices. Choice A is incorrect because it misinterprets higher 5-HT as reducing vmPFC valuation, which opposes the observed increase in delayed choices. When analyzing neurotransmitter effects, consider direct brain structure involvement and ensure conclusions align with observed data.

Question 9

Researchers examined the role of GABAergic inhibition in motor control using a within-subject design (n = 30). Participants received a single dose of a benzodiazepine (positive allosteric modulator of GABA-A receptors) or placebo on separate days before performing a finger-tapping sequence task requiring precise timing. fMRI analyses focused on the cerebellum and primary motor cortex (M1). Relative to placebo, benzodiazepine administration increased a peripheral index consistent with enhanced GABA-A activity, reduced cerebellar activation during error correction, and increased timing variability (worse precision). Which behavior change would be expected following neurotransmitter modulation, most consistent with the described brain structure involvement?

  1. Improved timing precision due to reduced inhibitory tone allowing greater cerebellar error correction
  2. Worsened timing precision consistent with enhanced GABAergic inhibition dampening cerebellar contributions to fine-tuned motor adjustment (correct answer)
  3. No effect on timing because GABA-A receptors are restricted to the peripheral nervous system
  4. Improved timing precision due to increased glutamate release in the hippocampus enhancing declarative memory for the sequence

Explanation: This question tests the understanding of the interaction between brain structures, neurotransmitters, and behavior. Neurotransmitters influence behavior by affecting brain structures, which mediate responses. In this vignette, GABA affects motor timing through the cerebellum. Choice B is correct because it accurately reflects the role of enhanced GABAergic inhibition in dampening cerebellar adjustments, worsening timing precision. Choice A is incorrect because it misinterprets reduced inhibitory tone as the outcome, which contradicts the enhanced GABA-A activity and increased variability. When analyzing neurotransmitter effects, consider direct brain structure involvement and ensure conclusions align with observed data.

Question 10

In a within-subject study, 28 participants received either a nicotinic acetylcholine receptor (nAChR) partial agonist or placebo before performing a sustained attention task with infrequent targets. EEG was recorded, and source localization emphasized right dorsolateral prefrontal cortex (dlPFC). The partial agonist increased target-evoked P300 amplitude and increased dlPFC source strength; behaviorally, hit rate increased with minimal change in false alarms. Which outcome is most consistent with the observed neurotransmitter and brain-structure effects?

  1. Decreased hit rate due to reduced dlPFC engagement following nAChR stimulation
  2. Increased hit rate due to enhanced cholinergic modulation of dlPFC networks supporting sustained attention (correct answer)
  3. Increased false alarms due to selective inhibition of GABA receptors in the cerebellum
  4. No behavioral change because acetylcholine primarily affects amygdala-mediated fear conditioning rather than attention

Explanation: This question tests the understanding of the interaction between brain structures, neurotransmitters, and behavior. Nicotinic acetylcholine receptors (nAChRs) enhance attentional processing, particularly in prefrontal cortical networks like the dorsolateral PFC (dlPFC). In this vignette, nAChR partial agonism increases dlPFC activity and P300 amplitude during target detection. Choice B is correct because it accurately reflects how enhanced cholinergic modulation of dlPFC networks improves sustained attention, leading to increased hit rates. Choice A is incorrect because nAChR stimulation enhances, not reduces, dlPFC engagement. When analyzing cholinergic effects on attention, remember that nicotinic receptor activation typically enhances prefrontal cortical function and improves attentional performance.

Question 11

Researchers investigated histamine signaling and wakeful exploration. In a randomized trial, 64 participants received either a first-generation H1 antihistamine or placebo before completing a virtual-environment exploration task that required learning the locations of novel objects. The behavioral outcomes were total distance explored and later recognition accuracy for object locations. fMRI focused on posterior parietal cortex (PPC) during exploration and hippocampus during retrieval. The antihistamine reduced PPC activation during exploration and reduced total distance explored, while hippocampal activation during retrieval was not significantly different after controlling for exploration time. Which outcome is most consistent with the observed neurotransmitter effects?

  1. Greater exploration and better location recognition due to increased histaminergic arousal under H1 blockade
  2. Reduced exploration with secondary reductions in location learning, consistent with diminished histamine-mediated arousal impacting PPC-guided exploration (correct answer)
  3. Improved location recognition because H1 blockade selectively enhances hippocampal long-term potentiation during retrieval
  4. No change in exploration because histamine primarily modulates spinal reflexes rather than cortical attention networks

Explanation: This question tests the understanding of the interaction between brain structures, neurotransmitters, and behavior. Histamine promotes wakefulness and arousal, with H1 receptors mediating cortical activation necessary for exploration and attention. In this vignette, H1 blockade reduces posterior parietal cortex (PPC) activation during exploration, affecting spatial behavior. Choice B is correct because it accurately reflects how diminished histamine-mediated arousal impairs PPC-guided exploration, leading to reduced exploration and secondary effects on location learning. Choice A is incorrect because H1 blockade reduces, not increases, histaminergic arousal. When analyzing antihistamine effects, consider that first-generation H1 blockers reduce cortical arousal and attention, impairing exploratory behavior and subsequent learning dependent on that exploration.

Question 12

In a lesion study, patients (n = 18) with bilateral hippocampal damage due to anoxia and matched controls (n = 18) completed a contextual fear learning task in which a distinct room context predicted an aversive noise. During learning, salivary cortisol was sampled as an index of hypothalamic–pituitary–adrenal (HPA) axis output, and startle responses were measured in the conditioned context versus a safe context. Controls showed increased cortisol and larger context-specific startle; hippocampal-damage patients showed preserved cortisol increases but reduced context-specific startle discrimination. How does the described brain structure influence behavior via neurotransmitter/hormone-linked activity, best explaining the dissociation?

  1. The hippocampus increases startle by elevating dopamine in the nucleus accumbens, which is sufficient for context discrimination
  2. The hippocampus is the primary generator of cortisol release, so hippocampal damage should eliminate cortisol responses entirely
  3. The hippocampus directly mediates skeletal muscle startle reflexes via spinal acetylcholine, independent of context
  4. The hippocampus supports encoding of contextual representations needed for discrimination, while HPA activation can occur without precise context mapping (correct answer)

Explanation: This question tests the understanding of the interaction between brain structures, neurotransmitters, and behavior. Neurotransmitters influence behavior by affecting brain structures, which mediate responses. In this vignette, cortisol and related hormones affect contextual fear through the hippocampus. Choice D is correct because it accurately reflects the role of the hippocampus in contextual encoding for discrimination, while HPA activation persists without it. Choice B is incorrect because it misinterprets the hippocampus as the primary cortisol generator, which does not explain preserved cortisol but reduced startle discrimination. When analyzing neurotransmitter effects, consider direct brain structure involvement and ensure conclusions align with observed data.

Question 13

In a neurotransmitter manipulation experiment, participants (n = 40) underwent acute tryptophan depletion (ATD) or a balanced amino acid control drink in a randomized crossover design. Two hours later, they completed an emotional interference task (naming the ink color of negative versus neutral words). Task-evoked fMRI focused on anterior cingulate cortex (ACC), and a validated proxy measure indicated reduced central serotonin availability after ATD. ATD led to increased reaction time slowing for negative words and increased ACC activation during negative trials relative to control. Which outcome is most consistent with the observed neurotransmitter effects?

  1. Reduced serotonin would be most consistent with increased dopamine in the substantia nigra selectively improving motor speed only
  2. Reduced serotonin would be most consistent with decreased ACC involvement and improved performance on negative trials
  3. Reduced serotonin would be most consistent with enhanced hippocampal long-term potentiation producing faster color naming
  4. Reduced serotonin would be most consistent with greater difficulty regulating negative interference, increasing ACC recruitment (correct answer)

Explanation: This question tests the understanding of the interaction between brain structures, neurotransmitters, and behavior. Neurotransmitters influence behavior by affecting brain structures, which mediate responses. In this vignette, serotonin affects emotional interference regulation through the ACC. Choice D is correct because it accurately reflects the role of reduced serotonin in increasing difficulty with negative interference, heightening ACC recruitment. Choice B is incorrect because it misinterprets reduced serotonin as decreasing ACC involvement and improving performance, which contradicts the increased slowing and activation. When analyzing neurotransmitter effects, consider direct brain structure involvement and ensure conclusions align with observed data.

Question 14

In a double-blind study, 60 healthy adults received either a single oral dose of a selective serotonin reuptake inhibitor (SSRI) or placebo 3 hours before completing a computerized go/no-go task during fMRI. The primary behavioral outcome was false alarms (responding on no-go trials), interpreted as reduced inhibitory control. fMRI analyses focused on ventromedial prefrontal cortex (vmPFC) and amygdala reactivity to negatively valenced distractor images presented between trials. The SSRI group showed reduced amygdala BOLD response to distractors and increased vmPFC–amygdala functional connectivity relative to placebo, while overall reaction time on go trials did not differ. Which behavior change is most consistent with these observed neurotransmitter and brain-structure effects?

  1. More false alarms on no-go trials due to heightened amygdala reactivity to negative distractors
  2. Fewer false alarms on no-go trials due to enhanced top-down regulation of amygdala responses by vmPFC (correct answer)
  3. No change in false alarms because serotonin primarily alters cerebellar timing rather than prefrontal control
  4. Fewer false alarms driven by increased dopamine release in the nucleus accumbens

Explanation: This question tests the understanding of the interaction between brain structures, neurotransmitters, and behavior. SSRIs increase serotonin availability, which enhances prefrontal cortex regulation of emotional responses mediated by the amygdala. In this vignette, increased serotonin affects inhibitory control through enhanced vmPFC-amygdala connectivity. Choice B is correct because it accurately reflects how SSRIs enhance top-down regulation by the vmPFC over amygdala reactivity, leading to better inhibitory control and fewer false alarms. Choice A is incorrect because it suggests increased amygdala reactivity, which contradicts the observed reduced amygdala BOLD response under SSRI. When analyzing neurotransmitter effects, consider how increased serotonin typically enhances prefrontal regulatory control over subcortical emotional structures, improving behavioral inhibition.

Question 15

A pharmacology experiment tested a selective -adrenergic receptor antagonist administered before a public-speaking stressor in 50 adults. Salivary alpha-amylase (an index correlated with sympathetic noradrenergic activation) and self-reported state anxiety were collected, and fMRI measured activity in the locus coeruleus (LC) and medial prefrontal cortex (mPFC) during anticipation. The antagonist reduced alpha-amylase and reduced LC activity, while mPFC activation during anticipation increased relative to placebo. Which behavior change is most consistent with the described neurotransmitter modulation and regional activity pattern?

  1. Higher state anxiety due to increased LC activity and reduced mPFC engagement during anticipation
  2. Lower state anxiety due to attenuated noradrenergic arousal from LC alongside greater mPFC regulatory engagement (correct answer)
  3. No change in anxiety because -adrenergic receptors primarily mediate gustatory processing in insular cortex
  4. Lower state anxiety due to increased dopamine release in the substantia nigra pars compacta

Explanation: This question tests the understanding of the interaction between brain structures, neurotransmitters, and behavior. β-adrenergic receptors mediate noradrenergic arousal responses, with the locus coeruleus (LC) as a primary source and the medial prefrontal cortex (mPFC) providing regulatory control. In this vignette, β-adrenergic blockade reduces LC activity and sympathetic arousal while increasing mPFC engagement. Choice B is correct because it accurately reflects how blocking β-adrenergic receptors attenuates noradrenergic arousal from the LC while enhancing mPFC regulatory engagement, leading to lower anxiety. Choice A is incorrect because the antagonist reduces, not increases, LC activity. When analyzing adrenergic modulation, consider that β-blockers reduce peripheral and central arousal while potentially enhancing prefrontal regulatory capacity.

Question 16

In a rodent lesion study, researchers produced excitotoxic lesions of the basolateral amygdala (BLA) in one group and sham surgery in another. After recovery, animals underwent cue-induced reinstatement of lever pressing for a previously extinguished sucrose reward. During reinstatement, in vivo microdialysis measured glutamate concentrations in the nucleus accumbens (NAc). BLA-lesioned animals showed blunted cue-induced increases in NAc glutamate and reduced reinstatement responding compared with sham animals, while baseline locomotion was similar. Which behavior change would be expected following the described brain structure damage and neurotransmitter change?

  1. Increased cue-induced lever pressing due to greater NAc glutamate release after BLA lesion
  2. Reduced cue-induced lever pressing due to diminished BLA-driven glutamatergic modulation of NAc during cue processing (correct answer)
  3. Unchanged reinstatement responding because cue-induced relapse depends primarily on cerebellar Purkinje cell output
  4. Reduced cue-induced lever pressing due to decreased serotonin release in the hippocampus during extinction recall

Explanation: This question tests the understanding of the interaction between brain structures, neurotransmitters, and behavior. The basolateral amygdala (BLA) sends glutamatergic projections to the nucleus accumbens (NAc) that are crucial for cue-induced reward seeking. In this vignette, BLA lesions reduce glutamate release in the NAc during cue presentation, affecting reinstatement behavior. Choice B is correct because it accurately reflects how BLA damage diminishes glutamatergic modulation of the NAc during cue processing, leading to reduced cue-induced lever pressing. Choice A is incorrect because BLA lesions decrease, not increase, NAc glutamate release. When analyzing brain circuit disruptions, consider that damage to upstream structures (BLA) reduces neurotransmitter release in downstream targets (NAc), impairing associated behaviors.

Question 17

A study evaluated the effect of acute opioid receptor activation on social pain. Forty participants were randomized to receive either a single dose of a -opioid receptor agonist or placebo before completing a task involving simulated social exclusion. The primary behavioral outcome was self-reported distress, and fMRI focused on dorsal anterior cingulate cortex (dACC) and anterior insula. Compared with placebo, the agonist group showed reduced dACC and anterior insula activation during exclusion and reported lower distress, without differences in general alertness. Which outcome is most consistent with the observed neurotransmitter effects?

  1. Higher distress due to increased dACC activation driven by opioid receptor stimulation
  2. Lower distress due to reduced dACC/anterior insula responses during exclusion following opioid receptor activation (correct answer)
  3. No change in distress because opioid signaling primarily affects occipital cortex visual processing
  4. Lower distress due to selective blockade of NMDA receptors in the hippocampus

Explanation: This question tests the understanding of the interaction between brain structures, neurotransmitters, and behavior. Opioid receptor activation modulates pain processing, including social pain, by affecting brain regions like the dACC and anterior insula. In this vignette, μ-opioid receptor activation reduces activity in these pain-processing regions during social exclusion. Choice B is correct because it accurately reflects how opioid receptor activation reduces dACC and anterior insula responses to social exclusion, leading to lower subjective distress. Choice A is incorrect because opioid receptor stimulation typically reduces, not increases, pain-related brain activation and distress. When analyzing opioid effects, remember that opioid receptor activation generally dampens both physical and social pain processing in overlapping neural circuits.

Question 18

Researchers tested whether blocking D2 dopamine receptors alters effort-based decision-making. In a randomized crossover design, 30 adults received either a low dose of a D2 antagonist or placebo on separate days before completing a task in which they chose between a low-effort/low-reward option and a high-effort/high-reward option. fMRI focused on ventral striatum (including nucleus accumbens) during choice. Under the D2 antagonist, participants showed reduced ventral striatal BOLD response to high-reward cues and selected the high-effort option less frequently; subjective ratings of reward magnitude were unchanged. Which behavior change would be expected following the described neurotransmitter modulation?

  1. Increased selection of high-effort options due to enhanced ventral striatal responsiveness to reward cues
  2. Decreased selection of high-effort options due to reduced dopaminergic signaling in ventral striatum during reward anticipation (correct answer)
  3. No change in effort-based choices because D2 receptors primarily regulate hippocampal episodic memory encoding
  4. Decreased selection of high-effort options due to increased serotonin signaling in the amygdala

Explanation: This question tests the understanding of the interaction between brain structures, neurotransmitters, and behavior. Dopamine signaling through D2 receptors in the ventral striatum is crucial for motivation and effort-based decision-making. In this vignette, blocking D2 receptors reduces dopaminergic signaling in the ventral striatum during reward anticipation. Choice B is correct because it accurately reflects how D2 antagonism reduces ventral striatal responsiveness to reward cues, leading to decreased motivation for high-effort options. Choice D is incorrect because the observed effects are specifically due to reduced dopamine signaling, not increased serotonin, and occur in the ventral striatum, not amygdala. When analyzing dopamine effects on motivation, consider that D2 receptor blockade typically reduces reward-seeking behavior by dampening striatal reward processing.

Question 19

Investigators examined 48 patients with focal bilateral hippocampal damage following an ischemic event and 48 matched controls. During PET imaging, participants completed a contextual fear-conditioning paradigm in which a neutral context was paired with an aversive sound. The primary behavioral outcome was context-specific freezing during a later test. PET quantification targeted hippocampus and amygdala and focused on norepinephrine (NE) release (indexed by displacement of an NE-sensitive radioligand) during acquisition. Patients with hippocampal damage showed preserved amygdala NE release during acquisition but reduced context-specific freezing at test compared with controls. Which statement best explains how the described brain structure influences behavior via neurotransmitter activity?

  1. The hippocampus is necessary for binding contextual cues to the amygdala-driven NE signal that supports later context-specific freezing (correct answer)
  2. The hippocampus directly generates NE release in the amygdala, so damage should abolish amygdala NE during acquisition
  3. Reduced freezing is best explained by impaired basal ganglia dopamine signaling that prevents motor output of fear
  4. The amygdala is required for explicit recall of the context, so preserved amygdala NE should normalize context memory

Explanation: This question tests the understanding of the interaction between brain structures, neurotransmitters, and behavior. The hippocampus is crucial for contextual memory formation, binding environmental cues to emotional responses mediated by the amygdala. In this vignette, norepinephrine release in the amygdala signals threat, but the hippocampus is needed to associate this signal with specific contexts. Choice A is correct because it accurately reflects the hippocampus's role in binding contextual information to amygdala-driven fear responses, explaining why hippocampal damage impairs context-specific freezing despite preserved amygdala NE. Choice B is incorrect because the hippocampus doesn't directly generate NE in the amygdala; NE is released by locus coeruleus projections. When analyzing brain structure interactions, remember that the hippocampus provides contextual information that guides when amygdala-mediated responses should be expressed.

Question 20

A brain lesion study examined patients (n = 22) with focal bilateral damage to the basolateral amygdala following surgical resection, compared with matched controls (n = 22). Participants completed a Pavlovian fear-conditioning paradigm in which a neutral tone (CS) was paired with a mild wrist shock (US). During acquisition, peripheral skin conductance responses (SCRs) to the CS were recorded, and cerebrospinal fluid (CSF) sampled post-task was assayed for norepinephrine (NE) metabolites as an index of locus coeruleus–NE system engagement. Controls showed increased NE metabolites and robust SCRs to the CS; the lesion group showed blunted NE metabolite increases and reduced SCR differentiation between CS+ and CS−. How does the described brain structure influence behavior via neurotransmitter activity, best explaining these findings?

  1. Amygdala damage enhances hypothalamic oxytocin signaling, increasing threat detection and SCRs to the CS
  2. Amygdala damage increases dopamine release in the nucleus accumbens, strengthening conditioned fear responses
  3. Amygdala damage primarily disrupts acetylcholine signaling in the cerebellum, reducing motor coordination during conditioning
  4. Amygdala damage reduces NE-linked arousal tagging of threat cues, weakening conditioned autonomic responses (correct answer)

Explanation: This question tests the understanding of the interaction between brain structures, neurotransmitters, and behavior. Neurotransmitters influence behavior by affecting brain structures, which mediate responses. In this vignette, norepinephrine affects fear conditioning through the amygdala. Choice D is correct because it accurately reflects the role of norepinephrine in arousal tagging via the amygdala, and its reduction weakens conditioned responses. Choice B is incorrect because it misinterprets amygdala damage as increasing dopamine in the nucleus accumbens, which would not explain blunted NE and reduced SCRs. When analyzing neurotransmitter effects, consider direct brain structure involvement and ensure conclusions align with observed data.