Advanced Movements Flashcards
why do humans have complex nervous systems?
as a way to navigate through an environment which is constantly changing
how do sea squirts nervous systems work?
- sea squirt larvae = more complex than its adult form
- has motor cord and brain-like ganglia
- upon finding a rock/stationary object, sea squirts become sessile, absorb much of its own brain and return to a rather primitive condition
what does cerebellum mean in Latin?
little brain
Graded and Competitive Goal Selection (selecting goals for actions) [Roitman and Shadlen]
-> looking at how our brains may respond to different quality of signal - we can look at the neurological activity and see what kind of quality of signal was received
-> wanted to see premotor areas responding to sensory cues which are enhanced or diminished based on the sensory cues involved
What happened in this experiment?
- Juice monkeys trained to respond visual signal and then choose a course of action in order to get a juice reward
- presented with two targets (T1 and T2) and they are presented with a target (loads of dots), they have to look at the correct location to get a juice reward
- In motion condition, you can vary the quality of the stimuli (no useful information, or subtle change indicating a direction which may indicate some kind of a reward (25% motion coherence (move in the right direction) or 50% motion coherence))
how can dispute the idea of free-will?
our brains particularly the premotor area, get ready to perform a motor act before we consciously decide to do something
what differences can we see in the monkey’s posterior parietal cortex? (Roitman and Shadlen, 2002)
when you differentiate brain activity based on the coherence of the signal
-> 50% highest firing rate, 25%, 5% chance level (and then 0% is last)
-> so any given time, more quality of information can prime your ultimate decision making on what to do next
what is sensorimotor transformation?
the process in which sensory stimuli are converted into motor commands
-> something needed to move, navigate the world and react to the environment
what requires a sensorimotor transformation?
a reflex -> gets converted in your nervous system into an actionable signal that your body makes
-> there are many types to: responds to sound, vision nd smell
what are two motor commands which require sensorimotor transformation and use the visual system?
reaching and grasping
how does reaching link to sensorimotor transformation?
system responsible for transforming visual information about the location of objects in extra personal space into the direction of a reaching movement
-> A path connects the parieto-occipital extrastriate area (PO) and the dorsal motor area (PMd)
how does the reaching system work?
PO connects with MDP (medial dorsal parietal), and MIP [codes the location of target you’re reaching for] (medial interparietal areas), eventually reach the PMD and allow you to reach in an appropriate direction
how does grasping link to sensorimotor transformation?
this system is responsible for transforming visual information about the properties of obkects, such as shape and size, into commands for effective grasping.
-> A path connects the dorsal and extrastriate (ES) cortext and the ventral premotor area (PMv)
how does the grasping system work?
Information fed back into primary motor cortex, and dorsal ES area and AIP (focus on shape size, orientation, including orientation of your hand), pre-motor area specifically works on grasping + a reminder that this is a constant flow of information
if the parietal area is damaged, there may be some issues. what is this condition called?
Optic Ataxia
-> anything behind the central sulcus seperating the frontal and parietal lobe can cause issues with this type of sensori-motor transformation
What is Optic Ataxia?
- an inability to reach and orientate your grip accurately under visual guidance (often like they’re reaching out in the dark)
- reaching accurately involves reaching in the right direction with the correct grip, scaling and grip orientation/finger placement
- visual guidance means being able to see both the target and the hand throughout
what is optic ataxia an issue with?
converting visual feedback into well actionable actions
-> not due to any basic sensory or motor deficit
what limbs can optic ataxia affect?
can affect one limb in one or both hemispheres (not purely visual or spatial) or can affect both or one limb in one hemisphere (not purely motor)
how does co-ordination work to reach a visual target?
- parietal cells represent location of visual stimuli]
- brain must transform between multiple coordinate systems to generate reaching to a visual target
double dissociations can tell us which part of the brain gets damaged in relation to visual tasks like this? what dies evidence help to tell us?
the parietal cortex helps the coordination of visual and position information for pre-motor areas
- dorsal ‘where’ stream is a pathway that allows us to form visually guided behaviour
- ventral ‘what’ pathway helps us with the ability to remember and identify things (ventral has strong connections with long term memory in the medial temporal lobe)
what can happen if you damage a specific parietal area
like optic ataxia
-> can describe what something is but not guide your hand towards it
what happens if your posterior parietal cortex is untouched, yet you damage the medial temporal lobe
your ability to describe would be severely disrupted
chains of movements are strung together with the intent to do what? (and what component is important for this)
to achieve a goal (and the supplementary motor cortex is important for this)
what is the supplementary motor cortex/area essential for?
self-generating movements
-> can draw on your stored repertoire of movements at any given point, irrespective of what’s going on in the environment
without the SMA what would happen?
we would no longer be able to perform well learned movements and rely on external cues to get things done
what could deactivation of SMA prodce?
severe disruption of learned sequences
what must there be a functional dissociation between to produce cued and uncued movements?
the pre-motor cortex and supplementary motor cortex
in the absence of explicit sensory cues, what is crucial?
for temporal structure of movement (SMA region)
-> And multiple movements or multiple motor programs can be relayed in a pre-determined (or determined) order
how can we measure the impact of knocking the system (SMA) out?
muscolo injections (an inhibitor of brain activity providing a temporal lesions in monkeys)
Cued sequences and learned sequences after a muscolo injection which is inhibiting this particular brain region
can see monkeys might learn an acute sequences (push, pull), show them a light to cue them and they will be able to do those actions in the correct sequence BUT if you ask them to perform a sequence they’ve learned previously, that has become reliant on the SMA then they create a lot more errors and we assume the size of the lesion/injection size would correlate with decreased performance on this task
-> functionable association here between the primates area, the supplementary motor areas and we can measure it depending on the particular tools and techniques we use
what size is the cerebellum?
small but highly folded and large surface area because of the sulci and gyri
can you read the cerebellum with fMRI?
difficult
-> relatively understudied for its importance and intrinsic role in certain aspects of our movement (due to the difficulty studying it)
what happens to the cerebellum if it’s damaged?
issues with co-ordination and voluntary motor movements, and ability to maintain balance and equilibrium
what is the basal ganglia?
group of subcortical nuclei responsible primarily for motor control, as well as other roles such as motor learning, executive functions and behaviors, and emotions
where is the cerebellum?
at the back of the brain, immediately inferior to the occipital and temporal lobes, and within the posterior cranial fossa.
-> It is separated from these lobes by the tentorium cerebelli, a tough layer of dura mater