L23 - subcortical control over eye movements

Which do the lateral rectus muscles do?

move the eyes horizontally to the periphery

What is EMG?

electromyography - tracks the electrical activity of eye muscles

What is EOG?

electroculography - tracks the movement of the eyes

What do the neurons in the deeper layers of the SC do?

are either visuomotor neurons with a visual field and movement field or are pure motor neurons with a movement field

What is a cell’s movement field?

the visual field that the eyes move to when the cell is active

How are SC neurons organised for motor movement?

smallest sacchades at the rostral (upper) SC and larger sacchades at the caudal SC

What are reflexive sacchades?

rapid eye movements to things which suddenly appear in our periphery

What was the effect of unilateral SC damage on reflexive sacchades?

patient had damage to right SC, she took a much longer time to orient towards stimuli on her left visual hemifield than in her right visual hemifield unlike rodents with SC damage who couldn’t orient towards a stimulus

What are reflexive eye movements?

SC plays an important role in generating reflexive eye movements, these are important for survival and allpow us to have incoming info project onto the fovea to optimise the visual detail

What are exogenous eye movements?

are triggered by the external environment, exogenous sacchades = reflexive sacchades

What are fixation cells?

found in the rostral SC, help us to fixate on a point and underlie the fixation reflex

Where are the sacchade cells?

caudal SC

What is the relationship between sacchades and fixation reflex?

are opponent processes as fixation cells help to maintain eye position and sacchade cells help to move eye position, when fixation cells are active inhibit sacchade cells to prevent eye movement and occurs both ways

What is the fixation offset paradigm and what do the results indicate for the fixation offset effect (FOE)?

measures strength of fixation reflex, half of trials are fixation overlap trials (both fixation stimulus and peripheral stimulus present), other half are fixation offset trials (only peripheral stimulus appears), found, fixation reflex causes fixation cells to inhibit sacchade cells, if large FOE indicates a strong fixation reflex, if small FOE indicates a weaker fixation reflex