L24 - subcortical control over eye movements

What are endogenous eye movements?

voluntary sacchades triggered internally

What is an endogenous eye movement task?

fixate on centre until arrow appears and move eyes in the direction arrow is pointing

What is the effect of TMS over cortex on sacchades and what was hypothesised?

endogenous sacchades: TMS over SPFC causes delays in sacchades towards the contralateral hemifield, but TMS over SPL had no effect on latency, exogenous sacchades: neither TMS over SPFC or SPL had an effect on latency, indicating the the SPFC important role for voluntary eye movements and hypothesised that TMS over SPFC disrupted normal frontal eye field

What did a study about frontal eye field (FEF) lesions find and confirm?

people with FEF lesions had delayed voluntary sacchades towards the contralesional hemifield but voluntary sacchades toward the ipsilesional hemifield were normal as vision is processed contralaterally, shows TMS over SPFC does disrupt FEF causing delays in contralateral endogenous sacchades

What structures do endogenous eye movements depend on?

cortical structures: the FEF which receives visual info indirectly and projects it towards the sacchade generators in the brain stem

What structures do exogenous eye movements depend more on?

subcortical structures: the superior colliculus receives visual info directly from the retina and projects it towards the sacchade generators in the brain stem

Are reflexive or voluntary eye movements faster and why?

reflexive as they require less processing so have fewer neural connections