Steven P. Wise

Prefrontal–parietal function: from foraging to foresight

Comparative neuroanatomy shows that new prefrontal areas emerged during the evolution of anthropoid primates to augment prefrontal, parietal, and temporal areas that had evolved in earlier primates. We recently proposed that the new anthropoid areas reduce foraging errors by generating goals from current contexts and learning to do so rapidly, sometimes based on single events. Among the contexts used to generate these goals, the posterior parietal cortex provides the new prefrontal areas with information about relational metrics such as order, number, duration, length, distance and proportion, which play a crucial role in foraging choices. Here we propose that this specialized network later became adapted to support the human capacity for reasoning and general problem-solving.

Encoding Goals but Not Abstract Magnitude in the Primate Prefrontal Cortex

Functional neuroimaging studies show that perceptual judgments about time and space activate similar prefrontal and parietal areas, and it is known that perceptions in these two cognitive domains interfere with each other. These findings have led to the theory that temporal and spatial perceptions, among other metrics, draw on a common representation of magnitude. Our results indicate that an alternative principle applies to the prefrontal cortex. Analysis at the single-cell level shows that separate, domain-specific populations of neurons encode relative magnitude in time and space. These neurons are intermixed with each other in the prefrontal cortex, along with a separate intermixed population that encodes the goal chosen on the basis of these perceptual decisions. As a result, domain-specific neural processing at the single-cell level seems to underlie domain generality as observed at the regional level, with a common representation of prospective goals rather than a common representation of magnitude.

Why is there a special issue on perirhinal cortex in a journal called hippocampus? The perirhinal cortex in historical perspective.

Despite its small size, the perirhinal cortex (PRh) plays a central role in understanding the cerebral cortex, vision, and memory; it figures in discussions of cognitive capacities as diverse as object perception, semantic knowledge, feelings of familiarity, and conscious recollection. Two conceptual constructs have encompassed PRh. The current orthodoxy incorporates PRh within the medial temporal lobe (MTL) as a memory area; an alternative considers PRh to be a sensory area with a role in both perception and memory. A historical perspective provides insight into both these ideas. PRh came to be included in the MTL because of two accidents of history. In evolutionary history, the hippocampus migrated from its ancestral situation as medial cortex into the temporal lobe; in the history of neuropsychology, a “memory system” that originally consisted of the amygdala and hippocampus came to include PRh. These two histories explain why a part of the sensory neocortex, PRh, entered into the conceptual construct called the MTL. They also explain why some experimental results seem to exclude a perceptual function for this sensory area, while others embrace perception. The exclusion of perceptual functions results from a history of categorizing tasks as perceptual or mnemonic, often on inadequate grounds. By exploring the role of PRh in encoding, representing, and retrieving stimulus information, it can be understood as a part of the sensory neocortex, one that has the same relationship with the hippocampus as do other parts of the neocortex that evolved at about the same time.

Outline for a Theory of Motor Behavior: Involving Cooperative Actions of the Cerebellum, Basal Ganglia, and Cerebral Cortex

Cerebellum means little brain. Cerebrum, of course, also means brain, but has come to refer primarily to the cerebral cortex and basal ganglia. One of the most vexing problems in brain physiology remains identifying the roles of these three structures in the selection and control of behavior. Unfortunately, researchers often study the cerebellum, cerebral cortex and basal ganglia independently. Indeed, many motor systems specialists often use the term “cortex” without modification despite the fact that both the forebrain and cerebellum have a cortex important in the control of movement. We set in this chapter, therefore, the objective of collective consideration of these three parts of the brain and their cooperative control functions. Our outline sketches one speculative view of how the cerebellum, basal ganglia and cerebral cortex might process information in a cooperative manner to establish goals, plan strategies and then program and implement a complex motor behavior.

Context-Dependent Duration Signals in the Primate Prefrontal Cortex

The activity of some prefrontal (PF) cortex neurons distinguishes short from long time intervals. Here, we examined whether this property reflected a general timing mechanism or one dependent on behavioral context. In one task, monkeys discriminated the relative duration of 2 stimuli; in the other, they discriminated the relative distance of 2 stimuli from a fixed reference point. Both tasks had a pre-cue period (interval 1) and a delay period (interval 2) with no discriminant stimulus. Interval 1 elapsed before the presentation of the first discriminant stimulus, and interval 2 began after that stimulus. Both intervals had durations of either 400 or 800 ms. Most PF neurons distinguished short from long durations in one task or interval, but not in the others. When neurons did signal something about duration for both intervals, they did so in an uncorrelated or weakly correlated manner. These results demonstrate a high degree of context dependency in PF time processing. The PF, therefore, does not appear to signal durations abstractedly, as would be expected of a general temporal encoder, but instead does so in a highly context-dependent manner, both within and between tasks.