LECTURE 27 - closed loop control : blindsight Flashcards
what is the extrageniculate visual pathway ?
aneural pathway in the brain that processes visual information that bypasses the primary visual cortex, (consists of a set of subcortical structures, including the superior colliculus, the pulvinar nucleus of the thalamus, and the accessory optic system)
what can happen if you have a leision to V1 ?
- blindness/partial blindness in one or both eyes
- scotoma and agnosia
- difficulty in perceiving motion, depth, and form
- visual hallucinations or distortions, such as seeing objects that aren’t there / misinterpreting the shape/size of objects
what is a scotoma ?
is a blind spot in the visual field
what is agnosia ?
impaired ability to recognize faces or objects
what is considered an “older pathways” that is dynamic and unexpected ?
extrageniculate pathway
what is a shorter pathway; V1 or extrageniculate pathway ?
extrageniculate (fewer synapses = shorter pathway)
what makes a pathway shorter ?
fewer synapses
what is saccade suppression ?
eyes moving at maximum velocity
what is the double-step paradigm ?
a technique used in neuroscience research to study the neural mechanisms underlying sensorimotor integration, attention, and decision-making
what do they do in the double-step paradigm ?
- adds a second target that appears briefly at a different location before the main target
- the timing of the appearance of the second target is manipulated to influence the saccade trajectory towards the main target.
in the double-step paradigm; 25% of trials =
target “jump” / pertubation
when does a target “jump” occur ?
occurs when eyes are moving at a maximum velocity
which paradigm uses a double step paradigm >
the double-step paradigm closed loop control
can people with lesions participate in this rapid ability to make that motor system connection (hands moving to the new target) ?
no they cannot
who preformed the double-step paradigm graphs ?
goodie et al.
what is backwards masking ?
renders a visual stimulus invisible by presenting a second stimulus shortly (e.g., 40 ms) after the first
describe the backwards masking experiment :
- presented a matrix of differently sized circles (4)
- had 4 red dots surrounding one circle (target circle)
- perception and action
- movement time decreases while target size increases
what type of phenomenon is present in the backwards masking experiment ?
an inverse phenomenon
what are the results when a mask is worn in the backwards masking experiment vs no mask …
movement time decreases while target size increases
when you mask the target during the backwards masking experiment what is there an emphasis in?
emphasis the four red dots
what was the perceptual task accuracy % results in the backwards masking experiment ?
no-mask = 96%
mask = 56% (basically guessing and perceptionally unaware)
how is the backwards masking experiment performed ?
- a technique used to study visual perception and consciousness
- involves presenting a brief visual stimulus, followed immediately by a second visual stimulus
- the mask is designed to interfere with the processing of the first stimulus by occupying the visual system and limiting the time available for the first stimulus to be perceived
- As a result, the first stimulus may not be consciously perceived, or may be perceived only partially or inaccurately
what are feedback delays ?
refer to the time delays that occur in the transmission of feedback signals in a closed-loop control system
dynamic + unexpected = ___ ms
75
who preformed the feedback delays experiment ?
zelaznik et al.
describe the zelaznik et al. experiment :
- participants completed vision or no vision aiming movements
- movements to be completed in 75 to 675 ms with or without vision
- turned lights off/on in a room and point at a target
- having people point in two movement times
which visual pathway takes longer due to more synapses ?
dorsal visual pathway
was there more or less errors with lights on ?
slightly less errors with lights on
