BRAIN PROCESSING Cortical information flow during flexible sensorimotor decisions
During flexible behavior, multiple brain regions encode sensory inputs, the current task, and choices. It remains unclear how these signals evolve…After a transient bottom-up sweep, there was a top-down flow of sustained task information from frontoparietal to visual cortex.
- Sensory information flowed from visual to parietal and prefrontal cortex.
- Choice signals developed simultaneously in frontoparietal regions and travelled to FEF and sensory cortex.
This suggests that flexible sensorimotor choices emerge in a frontoparietal network from the integration of opposite flows of sensory and task information.
Our reactions are not always the same to the same sensory input. Depending on context, we can map the same input onto different actions. This involves a distributed network of brain regions. During visuomotor decisions, choice predictive activity has been found in frontoparietal regions, including the lateral intraparietal area (LIP), prefrontal cortex (PFC), frontal eye fields (FEF), and motor and sensory cortex.
In sum, all types of information were encoded across the entire visuomotor pathway, albeit with different incidences and strength.
In summary, IT and V4 first extracted task information from the cues along with the encoding of cue identity. After this transient burst, there was a flow of sustained task information from PFC and LIP across the entire sensorimotor hierarchy.
- Motion information rose first in MT, followed by LIP, V4, IT, FEF, and PFC
- Color information rose first in MT, followed by V4, LIP, FEF, IT, and PFC
- Furthermore, color information appeared significantly earlier than motion information in V4, MT, PFC, and
Choice signals had a different dynamic……for all regions except IT, significant choice information preceded stimulus onset.
Our results instead suggest:
- a graded functional specialization of cortical regions with information shared between regions
- Second, sensory information flowed feed-forward from sensory cortex.
- Third, task information was first extracted in an early, transient burst in higher sensory cortex (V4 and IT).
- Fourth, choice predictive activity was present in sensory (V4 and MT), frontoparietal (LIP and PFC), and premotor (FEF) cortex before onset of the decision process. This suggests a link between spontaneous fluctuations of neuronal activity along the entire sensorimotor pathway and subsequent decisions.
- Fifth, choice signals first and simultaneously built up in PFC and LIP and then followed in FEF.
Our findings accord with previous reports of ramping choice predictive activity in LIP, PFC, and FEF but shed light on how choices are made in this network.
Our results suggest that, although sensory information reaches LIP and FEF before PFC, the accumulation of sensory evidence occurs first and jointly in LIP and PFC before decision signals are relayed to FEF.
In sum, flexible sensorimotor decisions are not a simple feed-forward process but result from complex temporal dynamics, including feed-forward and feedback interactions between frontal and posterior cortex.