426 research outputs found
Spatial and temporal distribution of visual information coding in lateral prefrontal cortex
Prefrontal neurons code many kinds of behaviourally relevant visual information. In behaving monkeys, we used a cued target detection task to address coding of objects, behavioural categories and spatial locations, examining the temporal evolution of neural activity across dorsal and ventral regions of the lateral prefrontal cortex (encompassing parts of areas 9, 46, 45A and 8A), and across the two cerebral hemispheres. Within each hemisphere there was little evidence for regional specialisation, with neurons in dorsal and ventral regions showing closely similar patterns of selectivity for objects, categories and locations. For a stimulus in either visual field, however, there was a strong and temporally specific difference in response in the two cerebral hemispheres. In the first part of the visual response (50β250 ms from stimulus onset), processing in each hemisphere was largely restricted to contralateral stimuli, with strong responses to such stimuli, and selectivity for both object and category. Later (300β500 ms), responses to ipsilateral stimuli also appeared, many cells now responding more strongly to ipsilateral than to contralateral stimuli, and many showing selectivity for category. Activity on error trials showed that late activity in both hemispheres reflected the animal's final decision. As information is processed towards a behavioural decision, its encoding spreads to encompass large, bilateral regions of prefrontal cortex
The Neuronal Basis of Visual Consciousness
Introduction: We outline in this chapter some of our present ideas about consciousness in
general and visual consciousness in particular. For now, we believe that the most
productive research strategy is to focus on the neuronal correlates of
consciousness (NCC). The next step is to establish the exact nature of the causal
relationship between neuronal events and subjective feelings and, finally, to
understand the thorny philosophical problem of qualia or subjective feelings and
how they can arise out of certain physical systems. We assume that higher
mammals, such as rodents or primates, share certain forms of sensory
consciousness with humans, even though these animals lack language skills.
To characterize the NCC, we have to contrast neural activity that directly
gives rise to conscious sensations, thoughts or action with neural activity that is
associated with unconscious, stereotyped and on-line visuo-motor behavior. Where
is the difference between these forms? How do these differences in activity
relate to the ventral and dorsal streams? We emphasize the importance of explicit
representations, the idea of essential nodes in a network and whether such nodes
correspond to the columnar properties of a patch of cortex. We also discuss
whether the correlated firing of a set of neurons is needed for consciousness and
the role of cortical area V1 and prefrontal areas in consciousness. We end by
briefly describing some of the relevant experiments. For earlier versions of these
ideas, see (Crick and Koch, 1998 and Koch and Crick, 2000)
Cognitive and Perceptual Functions of the Visual Thalamus
The thalamus is classically viewed as passively relaying information to the cortex. However, there is growing evidence that the thalamus actively regulates information transmission to the cortex and between cortical areas using a variety of mechanisms, including the modulation of response magnitude, firing mode, and synchrony of neurons according to behavioral demands. We discuss how the visual thalamus contributes to attention, awareness, and visually guided actions, to present a general role for the thalamus in perception and cognition
Adaptive Resonance Theory
SyNAPSE program of the Defense Advanced Projects Research Agency (Hewlett-Packard Company, subcontract under DARPA prime contract HR0011-09-3-0001, and HRL Laboratories LLC, subcontract #801881-BS under DARPA prime contract HR0011-09-C-0001); CELEST, an NSF Science of Learning Center (SBE-0354378
How Laminar Frontal Cortex and Basal Ganglia Circuits Interact to Control Planned and Reactive Saccades
The basal ganglia and frontal cortex together allow animals to learn adaptive responses that acquire rewards when prepotent reflexive responses are insufficient. Anatomical studies show a rich pattern of interactions between the basal ganglia and distinct frontal cortical layers. Analysis of the laminar circuitry of the frontal cortex, together with its interactions with the basal ganglia, motor thalamus, superior colliculus, and inferotemporal and parietal cortices, provides new insight into how these brain regions interact to learn and perform complexly conditioned behaviors. A neural model whose cortical component represents the frontal eye fields captures these interacting circuits. Simulations of the neural model illustrate how it provides a functional explanation of the dynamics of 17 physiologically identified cell types found in these areas. The model predicts how action planning or priming (in cortical layers III and VI) is dissociated from execution (in layer V), how a cue may serve either as a movement target or as a discriminative cue to move elsewhere, and how the basal ganglia help choose among competing actions. The model simulates neurophysiological, anatomical, and behavioral data about how monkeys perform saccadic eye movement tasks, including fixation; single saccade, overlap, gap, and memory-guided saccades; anti-saccades; and parallel search among distractors.Defense Advanced Research Projects Agency and the Office of Naval Research (N00014-95-l-0409, N00014-92-J-1309, N00014-95-1-0657); National Science Foundation (IRI-97-20333)
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