cognitive horizons 3

eye movements, attention and cognition

physiologically defined modules

defined in terms of what they process, and described in terms of their precise localisation

functionally defined modules

unconcerned with localisation, modules are hypothetical (theoretical, functionally defined)

Marr: different levels of analysis from physiology to computational accounts

not all phenomena can be explained at all levels. this can result in: physiologically plausible models that dont account for higher level cognitive functions, functional models that are unconstrained by physiology

evaluating theoretical concepts and empirical findings in cognitive neuroscience

integrating a wide range of evidence gives a better understanding of psychology. developing complex ideas and solving difficult problems is challenging and time consuming but also extrmeely rewarding and fun

eye movement control- the bigger picture

provides an insight into the relationship between biolgoy and cognitive psychology and an opportunity ti evaluate the contribution of neural mechanisms to higher cognitive functions

physiology of saccade generation

lots of different parts involved- superior colliculus deep insdei of brainstem, input from high level areas feed inot superior colliculus which feed into brain stem generator

brainstem saccade generator

firing of the pause and burst cells in the brainstem sacade generator ultimately determines firing of the motor neurones controlling when and where the eyes move

pause cells

stop firing 5-15 ms before and then during saccade, regular firing during fixation. receive inputs from the superior colliculus determining when the eyes move

burst cells

burst of activity just before and during saccade, cells specific to size and direction. recieve input from superior colliculus determining where the eyes move. silent before fixation and fire during saccade

motor neurone

pulse- step change in firing rate directly triggers saccade

superior colliculus

has low level input (bottom up) and higher level input. 3 dimensionla model- deep layer at bottom, intermediate layer and superifical layer at top

key inputs of superior colliculus

inputs: upper layers (bottom up, superficial layers)- visual projection from the retina and the visual cortex

lower layers (top dpwn, intermediate layers)- multi-sensory, higher cognitive influences

fovea

represented within central rostral pole (fixation neurones) and the 2 visual fields are topographically mapped within the left and right areas of the superior colliculus

superior colliculus: mapping

maps of visual space (superficial/ intermediate layers)

maps oculomotor space: cells soecific to direction and size of saccades (electrical stimulation triggers sacades)

deep layers of superior colliculus map oculomotor space, such that cells fire depending on the direction and size of saccades

Findlay and Walker

separation of when/ where pathways, higher level inputs incorporated all combine inot where and when we move our eyes

independence account

sequential attention model

pre-motor theory