Interacting with our environment is a complex task which requires to constantly weight and use different sources of information, whether they are sensory representation of the external world or cognitive, internally generated representation of our goals and expectations. For example, in order to detect a friend in a crowd, we compare sensory representation of what we are looking at (persons in the crowd) to representation of what we are looking for (our friend). This process, which I called comparative decision making, involves a large network of cortical and sub-cortical areas.
Sensory information are extracted along the hierarchy of cortical visual areas located in the occipital lobe of human and non-human primates. Cognitive representation about goal directed information are supported by several areas of the prefrontal cortex (PFC). Finally, in a recent series of studies, I’ve proposed that areas of posterior parietal cortex (PPC) plays a crucial role during comparative decision making. Specifically, I’ve proposed that PPC integrates two types of information:
1) Bottom up flow of sensory information. In this framework, PPC integrates and combine this sensory flow, which was previously gated by top-down attention (a signal originating in the prefrontal cortex and which gates behaviorally relevant visual information).
2) Top-down information, originating in PFC, about the identity of the stimuli being actively searched.
PPC then compares these information in order to encode a decision-related signal about the behavioral relevance of the stimuli.
The main goal of this project (ADMIN) is to directly test this hypothesis. I will record simultaneously the activity of large population of neurons from the visual cortex, from PFC and from PPC while NHP perform a task in which they have to compare visual and goal-directed information. This task, a modified version of a delayed-match to sample task, allow us to directly test 1) how information is kept in working memory and encoded in PFC; 2) how this signal is transformed into top-down signal modulating the bottom-up flow of sensory information and 3) how PPC integrates and compares bottom up and top down signals in order to participate to decision making processes.
This task, as well as the simultaneous recording of large populations of neurons in PPC, PFC and the visual cortex, will allow us to better understand how cognitive and sensory representation interact during decision-making. We will test (1) the computations performed by each cortical area as a function of the behavioral context, (2) how these cortical areas communicate, and (3) the role of the PPC in adapting our behavior to the different task demands. This will have an important impact on our understanding of deficits associated to PPC and PFC lesions and will help us redefined rehabilitation strategies.
