Brain Structure, Neurotransmitters, and Behavior (7A) - Psych & Soc

1. In a double-blind drug intervention study, healthy adults (n = 48) received either a single dose of a selective D2 receptor antagonist or placebo before completing a probabilistic reversal-learning task that requires updating stimulus–reward associations after contingencies switch. Task-evoked fMRI focused on the dorsal striatum (caudate/putamen), and microdialysis sampling (via an established PET proxy for synaptic dopamine release) was used to estimate task-related dopamine release in the dorsal striatum during the reversal phase. Relative to placebo, the antagonist group showed reduced dorsal striatal dopamine release and committed more perseverative errors (continued choosing the previously rewarded stimulus) after the contingency switch. Which behavior change would be expected following this neurotransmitter modulation, most consistent with the described brain structure involvement?
   Answer: More perseverative responding after the switch, reflecting reduced dopamine-dependent updating in the dorsal striatum 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 reversal learning through the dorsal striatum. Choice B is correct because it accurately reflects the role of reduced dopamine in impairing updating of stimulus-reward associations via the dorsal striatum, leading to perseverative errors. Choice A is incorrect because it misinterprets the antagonist's effect as increasing dopamine signaling, which contradicts the reduced release observed. When analyzing neurotransmitter effects, consider direct brain structure involvement and ensure conclusions align with observed data.
2. In a randomized trial, 50 participants received either a selective serotonin reuptake inhibitor (SSRI) for 14 days or no treatment before completing a punishment sensitivity task. The SSRI group showed increased activity in dorsal anterior cingulate cortex (dACC) during error trials and displayed greater post-error slowing (more cautious responding after mistakes). Reward responsiveness in ventral striatum was unchanged. Which outcome is most consistent with the observed neurotransmitter effects?
   Answer: Greater post-error slowing consistent with serotonergic enhancement of dACC-mediated performance monitoring 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 performance monitoring through the dorsal anterior cingulate cortex (dACC). Choice B is correct because it accurately reflects the role of serotonergic enhancement in increasing post-error slowing. Choice A is incorrect because it misinterprets serotonin as decreasing error monitoring, opposite to increased dACC activity. When analyzing neurotransmitter effects, consider direct brain structure involvement and ensure conclusions align with observed data.
3. 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?
   Answer: Lower state anxiety due to attenuated noradrenergic arousal from LC alongside greater mPFC regulatory engagement 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.
4. Researchers tested whether blocking histamine H1 receptors affects vigilance. Participants received either a first-generation antihistamine (H1 antagonist that crosses the blood–brain barrier) or placebo before completing a 30-minute psychomotor vigilance task. The hypothalamus was highlighted because histaminergic neurons in the tuberomammillary nucleus project broadly to cortex and support wakefulness. Compared with placebo, the antihistamine group showed slower reaction times and increased lapse frequency, with reduced hypothalamus-to-cortex functional connectivity. Which behavior change would be expected following neurotransmitter modulation?
   Answer: Slower responses and more lapses, consistent with reduced histaminergic arousal output from hypothalamus to cortical attention networks This question tests the understanding of the interaction between brain structures, neurotransmitters, and behavior. Histamine from hypothalamic neurons promotes wakefulness and vigilance through widespread cortical projections, with H1 receptors mediating arousal effects. In this vignette, blocking H1 receptors impairs vigilance performance and reduces hypothalamus-to-cortex connectivity. Choice B is correct because it accurately reflects how reduced histaminergic signaling from the hypothalamus impairs cortical arousal, leading to slower responses and attention lapses. Choice A is incorrect because H1 blockade reduces, not increases, histamine signaling and arousal. When analyzing neurotransmitter effects, consider how histaminergic systems from the hypothalamus maintain cortical arousal necessary for sustained attention.
5. A laboratory study measured cerebrospinal fluid (CSF) levels of gamma-aminobutyric acid (GABA) in 72 adults and assessed startle magnitude to unpredictable loud tones while participants viewed neutral images. Startle magnitude was recorded via orbicularis oculi electromyography. Functional MRI during the same session measured activity in the bed nucleus of the stria terminalis (BNST), a region implicated in sustained threat monitoring. Participants were stratified into Low, Medium, and High CSF GABA tertiles. Higher CSF GABA was associated with lower BNST activation and smaller startle responses, with no group differences in auditory acuity. Which outcome is most consistent with the observed neurotransmitter effects?
   Answer: High CSF GABA predicts reduced BNST activation and smaller startle due to greater inhibitory signaling This question tests the understanding of the interaction between brain structures, neurotransmitters, and behavior. GABA is the primary inhibitory neurotransmitter in the brain, reducing neural excitability in target regions. In this vignette, higher CSF GABA levels affect startle responses through inhibitory signaling in the BNST, a region involved in sustained threat monitoring. Choice B is correct because it accurately reflects how increased GABA produces greater inhibitory signaling, reducing BNST activation and consequently diminishing startle responses to unpredictable threats. Choice A is incorrect because GABA is inhibitory, not excitatory, so high levels would reduce rather than increase BNST activation. When analyzing GABA effects, remember that as an inhibitory neurotransmitter, higher levels typically reduce neural activity and associated behavioral responses.
6. In a double-blind, within-subject study, 28 healthy adults received either a single oral dose of a selective serotonin reuptake inhibitor (SSRI) or placebo before completing a probabilistic reversal-learning task during fMRI. Relative to placebo, SSRI increased BOLD signal in ventromedial prefrontal cortex (vmPFC) during negative feedback and reduced the number of perseverative errors after rule reversal. No significant change was observed in primary motor cortex activity. Which outcome is most consistent with the observed neurotransmitter effects?
   Answer: Improved behavioral flexibility mediated by enhanced serotonergic modulation of vmPFC feedback processing 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 reversal learning through the ventromedial prefrontal cortex (vmPFC). Choice B is correct because it accurately reflects the role of serotonin in mediating improved behavioral flexibility via enhanced vmPFC processing of negative feedback. Choice A is incorrect because it misinterprets the SSRI effect as reducing vmPFC engagement, contrary to the observed increase in BOLD signal and reduced errors. When analyzing neurotransmitter effects, consider direct brain structure involvement and ensure conclusions align with observed data.
7. In a pharmacology experiment, 26 participants received either a selective $5$-$\text{HT}_{2A}$ 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?
   Answer: Enhanced emotion regulation consistent with increased mPFC–amygdala coordination under serotonergic modulation 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.
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?
   Answer: More delayed-reward choices consistent with increased vmPFC engagement during future-oriented valuation under higher 5-HT tone 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.
9. A lab study tested whether increasing GABAergic signaling alters acute stress reactivity. Healthy participants received either a single dose of a benzodiazepine (a positive allosteric modulator at GABA-A receptors) or placebo before completing a public-speaking stressor. The investigators measured startle potentiation and recorded fMRI responses in the central nucleus of the amygdala (CeA), a region implicated in coordinating fear expression. Relative to placebo, the benzodiazepine group showed reduced startle potentiation and reduced CeA BOLD response during the speech preparation period, without changes in task comprehension. Which behavior change would be expected following neurotransmitter modulation?
   Answer: Reduced physiological arousal during the stressor, consistent with enhanced GABA-A–mediated inhibition in amygdala-dependent fear expression This question tests the understanding of the interaction between brain structures, neurotransmitters, and behavior. GABA is the primary inhibitory neurotransmitter, and benzodiazepines enhance GABA-A receptor function, increasing inhibition in fear-related circuits like the amygdala. In this vignette, benzodiazepine administration reduces both startle potentiation and central amygdala activity during stress. Choice B is correct because it accurately reflects how enhanced GABA-A-mediated inhibition in amygdala circuits reduces physiological arousal and fear expression. Choice A is incorrect because benzodiazepines increase, not reduce, inhibitory tone in the amygdala. When analyzing neurotransmitter effects, consider how enhancing inhibitory signaling reduces fear-related behavioral and neural responses.
10. 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?
    Answer: Decreased selection of high-effort options due to reduced dopaminergic signaling in ventral striatum during reward anticipation 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.
11. 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?
    Answer: Fewer false alarms on no-go trials due to enhanced top-down regulation of amygdala responses by vmPFC 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.
12. A study investigated aggression in 48 adults using an economic provocation task. Lower cerebrospinal fluid (CSF) 5-HIAA (a serotonin metabolite) was associated with higher reactive aggression scores and reduced functional coupling between orbitofrontal cortex (OFC) and amygdala during provocation. No association was found with motor cortex activity. Which outcome is most consistent with the observed neurotransmitter effects?
    Answer: Higher reactive aggression consistent with reduced serotonergic tone and weaker OFC regulation of amygdala responses 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 aggression through the orbitofrontal cortex (OFC) and amygdala. Choice A is correct because it accurately reflects the role of reduced serotonergic tone in increasing reactive aggression. Choice B is incorrect because it misinterprets reduced serotonin as increasing control, contrary to weaker OFC regulation. When analyzing neurotransmitter effects, consider direct brain structure involvement and ensure conclusions align with observed data.
13. 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?
    Answer: Lower distress due to reduced dACC/anterior insula responses during exclusion following opioid receptor activation 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.
14. A study examined impulsive choice in 45 adults using a delay discounting task. PET imaging indicated lower availability of dopamine transporters in ventral striatum was associated with steeper discounting (stronger preference for immediate rewards). Prefrontal cortical thickness measures were not associated with discounting in this sample. Which outcome is most consistent with the observed neurotransmitter effects?
    Answer: Steeper discounting is most consistent with altered dopaminergic signaling in ventral striatum affecting reward valuation 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 delay discounting through the ventral striatum. Choice D is correct because it accurately reflects the role of altered dopaminergic signaling in steeper reward discounting. Choice B is incorrect because it misinterprets the effect as involving GABA in the cerebellum, not relevant to the striatal findings. When analyzing neurotransmitter effects, consider direct brain structure involvement and ensure conclusions align with observed data.
15. 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?
    Answer: Reduced serotonin would be most consistent with greater difficulty regulating negative interference, increasing ACC recruitment 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.
16. In a within-subject experiment, 25 adults received caffeine (an adenosine receptor antagonist) or placebo before performing a sustained attention task. Caffeine increased activity in the ascending reticular activating system (ARAS) and increased functional connectivity between ARAS and thalamus. Participants reported less sleepiness and had fewer lapses of attention. Which behavior change would be expected following neurotransmitter modulation?
    Answer: Fewer lapses of attention consistent with disinhibition of arousal networks by adenosine receptor blockade 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, adenosine affects attention through the ascending reticular activating system (ARAS). Choice B is correct because it accurately reflects the role of adenosine blockade in disinhibiting arousal for fewer lapses. Choice A is incorrect because it misinterprets blockade as reducing arousal, opposite to the observed improvements. When analyzing neurotransmitter effects, consider direct brain structure involvement and ensure conclusions align with observed data.
17. 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?
    Answer: Higher target detection consistent with enhanced cholinergic modulation of thalamic relay and frontoparietal attention networks 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.
18. In a study of pain modulation, 30 participants received naloxone (an opioid receptor antagonist) or placebo prior to a placebo-analgesia paradigm. Naloxone reduced activation in periaqueductal gray (PAG) and rostral anterior cingulate cortex (rACC) during pain and eliminated the reduction in reported pain typically seen with placebo. Primary somatosensory cortex responses to stimulus intensity were unchanged. Which statement best explains the findings?
    Answer: Blocking opioid receptors disrupts descending analgesic control involving rACC and PAG, reducing placebo analgesia 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, opioids affect pain modulation through the periaqueductal gray (PAG) and rostral anterior cingulate cortex (rACC). Choice D is correct because it accurately reflects the role of opioid blockade in disrupting descending analgesia. Choice B is incorrect because it misinterprets naloxone as increasing opioid signaling, opposite to its antagonistic effect. When analyzing neurotransmitter effects, consider direct brain structure involvement and ensure conclusions align with observed data. Differentiate between primary sensory and modulatory pain pathways.
19. A study assessed the relationship between glutamate levels and habit expression. Participants learned a stimulus–response task that could be solved either by goal-directed strategies or by habits formed through repetition. Magnetic resonance spectroscopy measured glutamate in the dorsolateral striatum (putamen) after training. Individuals with higher putamen glutamate were more likely to persist with the learned response even after the outcome value was reduced (outcome devaluation), suggesting stronger habit control. Which outcome is most consistent with the observed neurotransmitter effects?
    Answer: More habitual responding after devaluation, consistent with excitatory signaling in dorsolateral striatal circuits supporting stimulus–response habits This question tests the understanding of the interaction between brain structures, neurotransmitters, and behavior. Glutamate is the primary excitatory neurotransmitter, and higher levels in the dorsolateral striatum strengthen stimulus-response associations that underlie habitual behavior. In this vignette, individuals with higher putamen glutamate show more habitual responding after outcome devaluation. Choice C is correct because it accurately reflects how excitatory signaling in dorsolateral striatal circuits supports the formation and expression of stimulus-response habits. Choice B is incorrect because glutamate increases, not decreases, synaptic efficacy in habit-related circuits. When analyzing neurotransmitter effects, consider how excitatory signaling in specific striatal regions promotes automatic, habitual responses.
20. In a double-blind, placebo-controlled study, healthy adults received either a single oral dose of a selective serotonin reuptake inhibitor (SSRI) or placebo 3 hours before completing a probabilistic reversal-learning task during fMRI. The task required participants to stop choosing a previously rewarded option after reward contingencies changed. Researchers focused on the orbitofrontal cortex (OFC) because of its role in updating stimulus–reward associations. Behavioral performance and BOLD signal in OFC were recorded. Compared with placebo, the SSRI group showed fewer perseverative errors after reversal and greater OFC BOLD response specifically during negative feedback trials (unexpected non-reward), without differences in baseline reaction time. Which outcome is most consistent with the observed neurotransmitter effects?
    Answer: Enhanced updating of choice strategy via increased OFC responsiveness to negative feedback, consistent with serotonin facilitating reversal learning This question tests the understanding of the interaction between brain structures, neurotransmitters, and behavior. Serotonin influences behavior by modulating brain regions involved in cognitive flexibility and learning from negative feedback. In this vignette, increased serotonin (via SSRI) enhances the OFC's responsiveness to negative feedback, facilitating reversal learning. Choice C is correct because it accurately reflects how serotonin helps update choice strategies through increased OFC activity during negative feedback, leading to fewer perseverative errors. Choice A is incorrect because it suggests reduced OFC engagement and increased perseveration, which contradicts the observed improvements. When analyzing neurotransmitter effects, consider how enhanced serotonin signaling promotes behavioral flexibility through increased cortical responsiveness to negative outcomes.

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