multi sensory processing - perception Flashcards
(25 cards)
What do the three semicircular canals detect?
Rotational head movements in the three orthogonal planes.
Which head‐motion detector senses linear acceleration up and down (gravity)?
The saccule.
Which structure detects linear acceleration side to side (horizontal gravity changes)?
The utricle.
What cellular elements transduce motion in the semicircular canals?
Hair cells whose cilia are deflected by endolymph fluid pressure on the cupula.
Describe the “push–pull” system in the vestibular canals.
Each canal is paired with its partner on the opposite side; when one canal’s firing rate increases (push), the other’s decreases (pull), enhancing sensitivity to rotation.
What is the primary role of vestibular information during locomotion?
To inform the brain about head motion and orientation, integrating with visual cues for stable perception.
How does retinal motion help us perceive movement when sitting in a moving car?
By providing optic flow—the pattern of motion across the retina that signals self‐motion relative to the scene.
What is optic flow?
The global pattern of relative motion between an observer and the environment; expansion, contraction, and laminar flow indicate movement direction and speed.
Where in the optic flow field does the brain infer the direction of self‐motion?
At the centre of expansion (or contraction), which is the point from which flow vectors radiate.
What four sensory/motor signals are integrated for stable spatial perception?
Visual input, vestibular signals, head‐movement signals, and body‐movement signals.
Which visual area (also called V5) is specialized for translation motion?
MT+ (middle temporal complex).
Why is MT+ alone insufficient for perceiving ego‐motion?
It encodes local translation motion but not the global patterns (expansion/contraction/rotation) characteristic of self‐motion.
Which area extends MT+ processing to optic‐flow patterns like expansion, contraction, and rotation?
MST (medial superior temporal area).
Name two additional cortical regions sensitive to ego‐motion.
The ventral intraparietal area (VIP) and the posterior insular cortex (PIC)
What is the torsional ocular reflex?
An involuntary eye rotation that compensates for head tilt, keeping gaze stable on a target by moving eyes equal and opposite to head roll.
In MST, how are visual and vestibular signals organized?
There are intermingled subpopulations of neurons: some respond purely to visual flow, some purely to vestibular input, and some to both.
What proportion of MST neurons fire when given compatible visual and vestibular cues?
pproximately 80% show enhanced firing under matched multisensory stimulation.
Define “congruent” and “opposite” multisensory neurons in MST.
Congruent neurons prefer visual and vestibular cues indicating the same heading direction; opposite neurons respond best when those cues conflict.
Give an example of a cell that fires only during head movement, regardless of eye movement.
A vestibular‐only neuron in MST that is unresponsive to visual flow but fires with angular acceleration of the head.
Give an example of a cell that fires only during eye movement, independent of head motion.
A visual‐only MST neuron tuned to the direction of retinal image motion, regardless of head movement.
Why is multisensory integration in the dorsal stream important for perception?
It “smooths out” noisy individual signals, yielding a coherent, stable experience of self‐motion and the visual world.
What inputs converge in the dorsal stream to support heading perception?
Inputs from MT+ (visual motion), vestibular nuclei, and proprioceptive/brainstem signals about head and body motion.
How does the brain resolve conflicts between visual and vestibular cues?
By weighted integration—cues are combined based on their reliability, down‐weighting less consistent signals.
What is the functional significance of having paired vestibular canals with push–pull dynamics?
It doubles sensitivity to rotations and helps detect the direction of head turns
