CiteULike: klouie's Cohen

An integrative theory of prefrontal cortex function.

EK Miller — 2006-01-23T23:03:09-00:00

Annu Rev Neurosci, Vol. 24 (2001), pp. 167-202.

The prefrontal cortex has long been suspected to play an important role in cognitive control, in the ability to orchestrate thought and action in accordance with internal goals. Its neural basis, however, has remained a mystery. Here, we propose that cognitive control stems from the active maintenance of patterns of activity in the prefrontal cortex that represent goals and the means to achieve them. They provide bias signals to other brain structures whose net effect is to guide the flow of activity along neural pathways that establish the proper mappings between inputs, internal states, and outputs needed to perform a given task. We review neurophysiological, neurobiological, neuroimaging, and computational studies that support this theory and discuss its implications as well as further issues to be addressed

Neuroeconomics.

George Loewenstein — 2007-11-15T13:58:41-00:00

Annu Rev Psychol (17 September 2007)

blacksquare, square, filled Abstract Neuroeconomics has further bridged the once disparate fields of economics and psychology. Such convergence is almost exclusively attributable to changes within economics. Neuroeconomics has inspired more change within economics than within psychology because the most important findings in neuroeconomics have posed more of a challenge to the standard economic perspective. Neuroeconomics has primarily challenged the standard economic assumption that decision making is a unitary process-a simple matter of integrated and coherent utility maximization-suggesting instead that it is driven by the interaction between automatic and controlled processes. This article reviews neuroeconomic research in three domains of interest to both economists and psychologists: decision making under risk and uncertainty, intertemporal choice, and social decision making. In addition to reviewing new economic models inspired by this research, we also discuss how neuroeconomics may influence future work in psychology. Expected final online publication date for the Annual Review of Psychology Volume 59 is November 30, 2007. Please see http://www.annualreviews.org/catalog/pubdates.aspx for revised estimates.

Non-invasive brain stimulation: a new strategy to improve neurorehabilitation after stroke?

Friedhelm Hummel — 2007-07-08T16:49:05-00:00

The Lancet Neurology, Vol. 5, No. 8. (August 2006), pp. 708-712.

SummaryBackground Motor impairment resulting from chronic stroke can have extensive physical, psychological, financial, and social implications despite available neurorehabilitative treatments. Recent studies in animals showed that direct epidural stimulation of the primary motor cortex surrounding a small infarct in the lesioned hemisphere (M1lesioned hemisphere) elicits improvements in motor function.Recent developments In human beings, proof of principle studies from different laboratories showed that non-invasive transcranial magnetic stimulation and direct current stimulation that upregulate excitability within M1lesioned hemisphere or downregulate excitability in the intact hemisphere (M1intact hemisphere) results in improvement in motor function in patients with stroke. Possible mechanisms mediating these effects can include the correction of abnormally persistent interhemispheric inhibitory drive from M1intact hemisphere to M1lesioned hemisphere in the process of generation of voluntary movements by the paretic hand, a disorder correlated with the magnitude of impairment. In this paper we review these mechanistically oriented interventional approaches.What next? These findings suggest that transcranial magnetic stimulation and transcranial direct current stimulation could develop into useful adjuvant strategies in neurorehabilitation but have to be further assessed in multicentre clinical trials.

What electrical microstimulation has revealed about the neural basis of cognition.

MR Cohen — 2007-06-11T17:10:47-00:00

Curr Opin Neurobiol, Vol. 14, No. 2. (April 2004), pp. 169-177.

Neurophysiologists have shown repeatedly that neural activity in different brain structures can be correlated with specific perceptual and cognitive functions, but the causal efficacy of the observed activity has generally been a matter of conjecture. By contrast, electrical microstimulation, which allows the experimenter to manipulate the activity of small groups of neurons with spatial and temporal precision, can now be used to demonstrate causal links between neural activity and specific cognitive functions. Here, we review this growing literature, including applications to the study of attention, visual and somatosensory perception, 'read-out' mechanisms for interpreting sensory maps, and contextual effects on perception. We also discuss potential applications of microstimulation to studies of higher cognitive functions such as decision-making and subjective experience.

Time Discounting for Primary Rewards

Samuel Mcclure — 2007-05-23T18:23:55-00:00

J. Neurosci., Vol. 27, No. 21. (23 May 2007), pp. 5796-5804.

Previous research, involving monetary rewards, found that limbic reward-related areas show greater activity when an intertemporal choice includes an immediate reward than when the options include only delayed rewards. In contrast, the lateral prefrontal and parietal cortex (areas commonly associated with deliberative cognitive processes, including future planning) respond to intertemporal choices in general but do not exhibit sensitivity to immediacy (McClure et al., 2004). The current experiments extend these findings to primary rewards (fruit juice or water) and time delays of minutes instead of weeks. Thirsty subjects choose between small volumes of drinks delivered at precise times during the experiment (e.g., 2 ml now vs 3 ml in 5 min). Consistent with previous findings, limbic activation was greater for choices between an immediate reward and a delayed reward than for choices between two delayed rewards, whereas the lateral prefrontal cortex and posterior parietal cortex responded similarly whether choices were between an immediate and a delayed reward or between two delayed rewards. Moreover, relative activation of the two sets of brain regions predicts actual choice behavior. A second experiment finds that when the delivery of all rewards is offset by 10 min (so that the earliest available juice reward in any choice is 10 min), no differential activity is observed in limbic reward-related areas for choices involving the earliest versus only more delayed rewards. We discuss implications of this finding for differences between primary and secondary rewards. 10.1523/JNEUROSCI.4246-06.2007

Separate neural systems value immediate and delayed monetary rewards.

SM McClure — 2006-02-22T21:51:30-00:00

Science, Vol. 306, No. 5695. (15 October 2004), pp. 503-507.

When humans are offered the choice between rewards available at different points in time, the relative values of the options are discounted according to their expected delays until delivery. Using functional magnetic resonance imaging, we examined the neural correlates of time discounting while subjects made a series of choices between monetary reward options that varied by delay to delivery. We demonstrate that two separate systems are involved in such decisions. Parts of the limbic system associated with the midbrain dopamine system, including paralimbic cortex, are preferentially activated by decisions involving immediately available rewards. In contrast, regions of the lateral prefrontal cortex and posterior parietal cortex are engaged uniformly by intertemporal choices irrespective of delay. Furthermore, the relative engagement of the two systems is directly associated with subjects' choices, with greater relative fronto-parietal activity when subjects choose longer term options.

Modulation of LIP activity by predictive auditory and visual cues.

YE Cohen — 2005-05-27T16:40:33-00:00

Cereb Cortex, Vol. 14, No. 12. (December 2004), pp. 1287-1301.

The lateral intraparietal area (area LIP) contains a multimodal representation of extra-personal space. To further examine this representation, we trained rhesus monkeys on the predictive-cueing task. During this task, monkeys shifted their gaze to a visual target whose location was predicted by the location of an auditory or visual cue. We found that, when the sensory cue was at the same location as the visual target, the monkeys' mean saccadic latency was faster than when the sensory cue and the visual target were at different locations. This difference in mean saccadic latency was the same for both auditory cues and visual cues. Despite the fact that the monkeys used auditory and visual cues in a similar fashion, LIP neurons responded more to visual cues than to auditory cues. This modality-dependent activity was also seen during auditory and visual memory-guided saccades but to a significantly greater extent than during the predictive-cueing task. Additionally, we found that the firing rate of LIP neurons was inversely correlated with saccadic latency. This study indicates further that modality-dependent differences in LIP activity do not simply reflect differences in sensory processing but also reflect the cognitive and behavioral requirements of a task.

A common reference frame for movement plans in the posterior parietal cortex.

YE Cohen — 2005-02-08T20:36:24-00:00

Nat Rev Neurosci, Vol. 3, No. 7. (July 2002), pp. 553-562.

Orchestrating a movement towards a sensory target requires many computational processes, including a transformation between reference frames. This transformation is important because the reference frames in which sensory stimuli are encoded often differ from those of motor effectors. The posterior parietal cortex has an important role in these transformations. Recent work indicates that a significant proportion of parietal neurons in two cortical areas transforms the sensory signals that are used to guide movements into a common reference frame. This common reference frame is an eye-centred representation that is modulated by eye-, head-, body- or limb-position signals. A common reference frame might facilitate communication between different areas that are involved in coordinating the movements of different effectors. It might also be an efficient way to represent the locations of different sensory targets in the world.