Sensorimotor Intergration

why have animals evolved brains?

to generate meaningful movement (behaviour)

the monosynaptic stretch reflex

1. Stretch of the mechanoreceptors in the muscle increase firing rate of the afferent sensory neuron.

2. Increased neurotransmitter release activates the motor neuron.

3. Contraction of biceps muscle.

what is contralateral movement?

voluntary movement

what is ipsilateral movement?

reflex movement

polysynaptic reflex and interaction with CNS

neural pathways and structures underlying voluntary movements

visual system (visual attention and saccades) → integration of visual information → trajectory prediction → movement control → movement precision → muscle contraction

how does the visual system detect stimuli?

• cones in the fovea detect the light bouncing off of the stimulus

• photoreceptors transduce the stimulation into neural activity

• bipolar cells change the activation state of ganglion cells → conveys visual info to the brain

how can the content of a person’s visual attention be traced?

from the course of that person’s saccades (neurons in the posterior parietal cortex fire more vigorously when the visual stimulus are the target of saccades)

what is the function of the saccade system?

to keep the image of the stimulus in the fovea (where vision is most accurate) (check slides for more info)

what are the two pathways involved in the integration of visual information?

geniculostriate pathway; tectopulvinar pathway

what occurs in the geniculostriate pathway?

• Perception of motion and depth by the dorsal visual stream (how).

• Perception of contrasts, contour and colour by the ventral visual pathway \n (what).

what occurs in the tectopulvinar pathway?

* perception of the location by the pulvinar pathway (where)

what is trajectory prediction?

the integration of information over time; prior information about the stimulus is used (memory) as well as sensoria; integration to produce a likelihood about the situation

where does movement control occur in the brain?

basal ganglia

what does the oculomotor loop do?

controls eye movement and tracking of the stimulus

what does the skeletomotor loop do?

controls voluntary movements

what does the basal ganglia do (in terms of movement control)?

• action selection

• initiation and terminating actions

• relating actions with consequences

how is the cerebellum involved in movement precision?

some regions of the cerebellum are activated when eye tracking and hand movement requires coordination

what happens during muscle contraction (neuromuscular junction)?

Acetylcholine release by the motor neuron axon terminal will contract fibres in the target muscle

how does the reward system affect behaviour/movement?

depending on the outcome of the behavioural reaction, it will either modulate the maintenance or modify the behavioural action