PubMed Health⌕ Search

Biomedical subjects

Gregory S Berns

Publications and source records attributed to Gregory S Berns.

15 recordsLinked to original sources

Neurobiological substrates of dread.

Given the choice of waiting for an adverse outcome or getting it over with quickly, many people choose the latter. Theoretical models of decision-making have assumed that this occurs because there is a cost to waiting-i.e., dread. Using functional magnetic resonance imaging, we measured the neural responses to waiting for a cutaneous electric shock. Some individuals dreaded the outcome so much that, when given a choice, they preferred to receive more voltage rather than wait. Even when no decision was required, these extreme dreaders were distinguishable from those who dreaded mildly by the rate of increase of neural activity in the posterior elements of the cortical pain matrix. This suggests that dread derives, in part, from the attention devoted to the expected physical response and not simply from fear or anxiety. Although these differences were observed during a passive waiting procedure, they correlated with individual behavior in a subsequent choice paradigm, providing evidence for a neurobiological link between the experienced disutility of dread and subsequent decisions about unpleasant outcomes.

Adult↗

Human striatal activation reflects degree of stimulus saliency.

Salient stimuli are characterized by their capability to perturb and seize available cognitive resources. Although the striatum and its dopaminergic inputs respond to a variety of stimuli categorically defined as salient, including rewards, the relationship between striatal activity and saliency is not well understood. Specifically, it is unclear if the striatum responds in an all-or-none fashion to salient events or instead responds in a graded fashion to the degree of saliency associated with an event. Using functional magnetic resonance imaging, we measured activity in the brains of 20 participants performing a visual classification task in which they identified single digits as odd or even numbers. An auditory tone preceded each number, which was occasionally, and unexpectedly, substituted by a novel sound. The novel sounds varied in their ability to interrupt and reallocate cognitive resources (i.e., their saliency) as measured by a delay in reaction time to immediately subsequent numerical task-stimuli. The present findings demonstrate that striatal activity increases proportionally to the degree to which an unexpected novel sound interferes with the current cognitive focus, even in the absence of reward. These results suggest that activity in the human striatum reflects the level of saliency associated with a stimulus, perhaps providing a signal to reallocate limited resources to important events.

Acoustic Stimulation↗

Anterior cingulate activation and error processing during interferon-alpha treatment.

BACKGROUND: There has been increasing interest in the role of immunologic processes, notably cytokines, in the development of behavioral alterations, especially in medically ill patients. Interferon (IFN)-alpha is notorious for causing behavioral symptoms, including depression, fatigue, and cognitive dysfunction, and has been used to investigate the effects of cytokines on the brain. METHODS: In the present study we assessed the effects of low-dose IFN-alpha on brain activity, using functional magnetic resonance imaging during a task of visuospatial attention in patients infected with hepatitis C virus (HCV). RESULTS: Despite endorsing symptoms of impaired concentration and fatigue, IFN-alpha-treated patients (n = 10) exhibited task performance and activation of parietal and occipital brain regions similar to that seen in HCV-infected control subjects (n = 11). Interestingly, however, in contrast to control subjects, IFN-alpha-treated patients exhibited significant activation in the dorsal part of the anterior cingulate cortex (ACC), which highly correlated with the number of task-related errors. No such correlation was found in control subjects. CONCLUSIONS: Consistent with the role of the ACC in conflict monitoring, ACC activation during IFN-alpha administration suggests that cytokines might increase processing conflict or reduce the threshold for conflict detection, thereby signaling the need to exert greater mental effort to maintain performance. Such alterations in ACC activity might in turn contribute to cytokine-induced behavioral changes.

Adult↗

Neurobiological correlates of social conformity and independence during mental rotation.

BACKGROUND: When individual judgment conflicts with a group, the individual will often conform his judgment to that of the group. Conformity might arise at an executive level of decision making, or it might arise because the social setting alters the individual's perception of the world. METHODS: We used functional magnetic resonance imaging and a task of mental rotation in the context of peer pressure to investigate the neural basis of individualistic and conforming behavior in the face of wrong information. RESULTS: Conformity was associated with functional changes in an occipital-parietal network, especially when the wrong information originated from other people. Independence was associated with increased amygdala and caudate activity, findings consistent with the assumptions of social norm theory about the behavioral saliency of standing alone. CONCLUSIONS: These findings provide the first biological evidence for the involvement of perceptual and emotional processes during social conformity.

Adult↗

Human striatal responses to monetary reward depend on saliency.

While the striatum has been implicated in reward processing, an alternative view contends that the striatum processes salient events in general. Using fMRI, we investigated human striatal responses to monetary reward while modulating the saliency surrounding its receipt. Money was maximally salient when its receipt depended on a correct response (active) and minimally salient when its receipt was completely independent of the task (passive). The saliency manipulation was confirmed by skin conductance responses and subjective ratings of the stimuli. Significant caudate and nucleus accumbens activations occurred following the active compared to passive money. Such activations were attributed to saliency rather than the motor requirement associated with the active money because striatal activations were not observed when the money was replaced by inconsequential, nonrewarding stimuli. The present study provides evidence that the striatum's role in reward processing is dependent on the saliency associated with reward, rather than value or hedonic feelings.

Adolescent↗

Something funny happened to reward.

The human reward system has been shown to be activated by a wide range of reinforcers, including food, money, sex, drugs, and beauty. Now, a recent fMRI study has found mesolimbic reward activation associated with humorous cartoons, providing a neurobiological link between theories of humour and hedonic processes in the brain.

Brain Mapping↗

The neurobiology of bipolar disorder.

The neurobiology of bipolar disorder is reviewed. Bipolar disorder is associated with alterations in central nervous system (CNS) function from the level of large-scale brain circuits to intracellular signal transduction mechanisms. Because of the broad spectrum over which these abnormalities appear, the causative effects are most likely present in the lowest common denominator of all of these systems. Current evidence points to subtle alterations in signal transduction that reverberate downstream both intra- and extracellularly to produce the symptoms of bipolar disorder.

Bipolar Disorder↗

Human striatal response to salient nonrewarding stimuli.

Although one proposed function of both the striatum and its major dopamine inputs is related to coding rewards and reward-related stimuli, an alternative view suggests a more general role of the striatum in processing salient events, regardless of their reward value. Here we define saliency as an event that both is unexpected and elicits an attentional-behavioral switch (i.e., arousing). In the present study, human striatal responses to nonrewarding salient stimuli were investigated. Using functional magnetic resonance imaging (fMRI), the blood oxygenation level-dependent signal was measured in response to flickering visual distractors presented in the background of an ongoing task. Distractor salience was manipulated by altering the frequency of distractor occurrence. Infrequently presented distractors were considered more salient than frequently presented distractors. We also investigated whether behavioral relevance of the distractors was a necessary component of saliency for eliciting striatal responses. In the first experiment (19 subjects), the distractors were made behaviorally relevant by defining a subset of them as targets requiring a button press. In the second experiment (17 subjects), the distractors were not behaviorally relevant (i.e., they did not require any response). The fMRI results revealed increased activation in the nucleus accumbens after infrequent (high salience) relative to frequent (low salience) presentation of distractors in both experiments. Caudate activity increased only when the distractors were behaviorally relevant. These results demonstrate a role of the striatum in coding nonrewarding salient events. In addition, a functional subdivision of the striatum according to the behavioral relevance of the stimuli is suggested.

Adult↗

Temporal prediction errors in a passive learning task activate human striatum.

Functional MRI experiments in human subjects strongly suggest that the striatum participates in processing information about the predictability of rewarding stimuli. However, stimuli can be unpredictable in character (what stimulus arrives next), unpredictable in time (when the stimulus arrives), and unpredictable in amount (how much arrives). These variables have not been dissociated in previous imaging work in humans, thus conflating possible interpretations of the kinds of expectation errors driving the measured brain responses. Using a passive conditioning task and fMRI in human subjects, we show that positive and negative prediction errors in reward delivery time correlate with BOLD changes in human striatum, with the strongest activation lateralized to the left putamen. For the negative prediction error, the brain response was elicited by expectations only and not by stimuli presented directly; that is, we measured the brain response to nothing delivered (juice expected but not delivered) contrasted with nothing delivered (nothing expected).

Adult↗

Neural correlates of the complexity of rhythmic finger tapping.

Using functional magnetic resonance imaging (fMRI), we studied the neural correlates of the complexity of rhythmic finger tapping. Our experiments measured the brain activity of 13 subjects performing rhythmic tapping on a response box with multistable rhythms of 1 to 5 different interresponse intervals. From the button press response times, we constructed phase portraits where we identified the number of clusters of periodic points in a rhythm that corresponded to the number of different beats of the rhythm performed. We then constructed a statistical model for correlation analysis involving the following behavioral parameters: rate of tapping and number of beats in a rhythm. The tapping rate correlated with the brain activity in the ipsilateral pre/postcentral gyrus, and the number of beats (complexity) was correlated with activations in the primary motor cortex, supplementary motor area, basal ganglia, thalamus, and cerebellum. A region of interest (ROI) average analysis showed that the complexity of a rhythm had a differential correlation with the activity in these regions. The cerebellum and the thalamus showed increasing activity, and the basal ganglia showed decreasing activity with complexity of a rhythm. These results identify the areas involved in a rhythm generation and the modulation of brain activity with the complexity.

Adult↗

Neural economics and the biological substrates of valuation.

A recent flurry of neuroimaging and decision-making experiments in humans, when combined with single-unit data from orbitofrontal cortex, suggests major additions to current models of reward processing. We review these data and models and use them to develop a specific computational relationship between the value of a predictor and the future rewards or punishments that it promises. The resulting computational model, the predictor-valuation model (PVM), is shown to anticipate a class of single-unit neural responses in orbitofrontal and striatal neurons. The model also suggests how neural responses in the orbitofrontal-striatal circuit may support the conversion of disparate types of future rewards into a kind of internal currency, that is, a common scale used to compare the valuation of future behavioral acts or stimuli.

Animals↗

Measurements of brain activity complexity for varying mental loads.

Using functional magnetic resonance imaging, we investigate the variation in dynamical complexity of human brain activity for different mental loads. Our experiments measured the activity of ten subjects under three experimental conditions: a rest condition, a periodic task of finger opposition, and a task of finger opposition alternated with mathematical serial calculation. We used the correlation dimension to gauge the spatiotemporal complexity of brain activity. The experiments show a direct relationship between this complexity and the difficulty of the task. A natural interpretation is that higher levels of mental load recruit a larger number of independent neural processes that contribute to complex brain dynamics. These results suggest the possibility that the relative change in correlation dimension can be a useful global measure of brain dynamics, e.g., in determining the levels of mental activity, even if little is known about the underlying neurological processes.

Adult↗

Hyperscanning: simultaneous fMRI during linked social interactions.

"Plain question and plain answer make the shortest road out of most perplexities." Mark Twain-Life on the Mississippi. A new methodology for the measurement of the neural substrates of human social interaction is described. This technology, termed "Hyperscan," embodies both the hardware and the software necessary to link magnetic resonance scanners through the internet. Hyperscanning allows for the performance of human behavioral experiments in which participants can interact with each other while functional MRI is acquired in synchrony with the behavioral interactions. Data are presented from a simple game of deception between pairs of subjects. Because people may interact both asymmetrically and asynchronously, both the design and the analysis must accommodate this added complexity. Several potential approaches are described.

Brain↗

Activity in human ventral striatum locked to errors of reward prediction.

The mesolimbic dopaminergic system has long been known to be involved in the processing of rewarding stimuli, although recent evidence from animal research has suggested a more specific role of signaling errors in the prediction of rewards. We tested this hypothesis in humans, using functional magnetic resonance imaging (fMRI) and an operant conditioning paradigm for the discrete delivery of small quantities of fruit juice, along with a control experiment in which juice was substituted with a neutral visual stimulus. A local estimation of the activity in the ventral striatum showed a significant differentiation when the juice was withheld at the expected time of delivery; this finding was not replicated in the case of visual stimulation, providing evidence for time-locked processing of reward prediction errors in human ventral striatum.

Adult↗

Limbic hyperreactivity in bipolar II disorder.

OBJECTIVE: The authors' goal was to determine whether patients with bipolar II disorder had altered regional brain responses to novel motor sequences. METHOD: Regional cerebral blood flow was measured with positron emission tomography in 13 patients with bipolar II disorder and 14 healthy comparison subjects. Participants performed a serial reaction time task in which they were visually cued to press one of four buttons at a time. The order of button presses was determined by a complex sequence that was changed in the latter half of the study. RESULTS: In the comparison subjects a spatial attention circuit in the superior parietal lobe and supplementary motor area was activated in response to the introduction of the new sequence. Patients did not display this activation pattern; instead, a widespread limbic network was activated in response to the new sequence. CONCLUSIONS: The attentional resources of patients with bipolar II disorder are not reallocated when they are confronted with a nonemotional motor task; rather, their performance is altered through activation of limbic circuitry.

Adult↗