Biological Network underlying fast task-specific reactions.
A proposal on the respective roles of Parietal and Premotor Cortex, Frontal Cortex and Cerebellum
Centre for Neural and Adaptive Systems
School of Computing
University of Plymouth
1. What is the fastest route from the visual system
to the motor output?
V1 -> PO -> MIP -> Pre-Motor -> Motor Cortex
(for arm movements)
V1 -> PO -> LIP -> FEF -> Superior Colliculus
(for eye movements)
|Areas (from 1)||v1||PO||PPC (MIP)||PM||M1|
|Latencies (from 2)||65 ms||70 ms (values for MT used)||72 ms (values of FEF/MST used)||?||?|
2. Role of MIP ? (Kalaska & Crammond, 1995)
Proposal based on (3):3. Role of PM ?
"MIP knows WHAT action is to be performed as indicated by the visual stimulus and the current task"
No decisions as to the execution of the response, only sensory-motor mapping.
PPC lesions: Inability to set-up a response rule.
Proposal based on (3):4. How does PM know when to enable actions ?
"PM acts as a relay between PPC and M1, and acts upon PFC signals telling WHEN to perform the action"
Pre-frontal cortex exerts general inhibitory control. (Braun et al., 1992) , possibly using object-specific information from IT (slow visual pathway).5. How does MIP know which mapping to apply?
Many inputs to MIP: - M1 and PM
- PFC (46)
- Visual areas (IT)
Imaging studies: The cerebellum sends sensory – motor maps to the PPC (Le et all, 1998)
Lesion studies: Cerebellar lesions cause deficits in applying motor response rules.
-> Proposal: Role of Lateral Cerebellum is setting up task-specific
sensory-motor associations in PPC
6. How does the cerebellum know which is the current task?
Many inputs to the Cerebellum : - PPC7. Computational implications.
- Motor cortices
Imaging studies: Fronto-Polar Prefrontal Cortex (area 10) (Koechlin et al, 1999, Nature) is active when switching between two tasks is required. Area 10 projects to cerebellum (exact target sub-area unknown). Could be the source of task specification signals.
Lesion of FPPFC has similar effects as PPC lesions.
Download: "Planning Behaviours" extendend abstract of presentation at the Emernet Workshop, Edinburgh 15 Sept. 1999
"Role of the cerebellum in time-critical goal-oriented behaviour: Anatomical basis and control principle." ps.zip (250.872) PDF (111.833)
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