Adrian Owens Research

Transcription

1 *Classic View: Not entirely correct Nervous System Central Nervous System is made up of the brain and the spinal cord. Peripheral Nervous System is broken down into a component called the somatic division. Stretch information is received to the CNS through the somatic division in PNS. Allows connectivity with CNS Hierarchical Organization of the Central Nervous system: *The Hierarchy: Think of the Cerebral Cortex as the big boss, it tells everyone else what to do and when to do it Think of the thalamus, basal ganglia, pons, and cerebellum as being second in command The brainstem is third in command All signals must travel through brainstem to get to spinal cord It s a relay. Just conveys information Doesn t do anything in terms of modifying signals The spinal cord is a slave system to all the above. When someone has a problem with their cerebral cortex, they cannot do precision movements but on power (gross) movement Can only move hands and fingers at same time. Can t pitch. If brainstem is lesion, become locked-in. Because no signals can be sent to spinal cord, you know what is going on around you but cant respond. Appear dead Luigi Galvani (18 th Century): Was interested in how muscles contract Before it was believed that movement would occur by fluid in the body moved Attached lightening rod to spinally prepared frogs and when there was a thunderstorm, the frog would move. The Neuron: It is believed that when young learn new skill, they develop more neurons In adults, it is a new neural pathway to cause movement. This is done by more dendrite and axon terminals This is done by repeated practice Myelin Sheath: allows for quicker electrical travel Different types of neuron, have different thickness allowing for different speeds of conduction Adrian Owens Research Watch diving bell and butterfly

2 Motor unit: Neuron and all muscle fibers in contact AMN disease- damage in neuron in motor cortex- cerebral cortex Speed of Nerve Conduction: Helmholtz (1850s): Interested in speed of nerve conduction Used isolated muscle and motor nerve of a frog Measured time between electrical stimulation and muscle contraction He would isolate a muscle in a frog. Would get direct access through CNS through the spinal cord and timed the amount of time needed for the contraction. He would put the stimulus far away from cell body and close. By knowing how long they took to contract and the differences between the contractions, he could find out how quickly it was travelling. Very accurate Helmoholtz Findings:

3 Estimate speed of human nerve conduction Measured reaction time in response to electrical stimulus to two points (e.g. foot, thigh) Nerve conduction velocity very fast (35-60 m/s) That speed is about 1/10 the speed of sound (speed of sound= 1238 km/h) Diseases of the nerve: 1. Disease of the nerve influences amplitude of nerve conduction E.g. Amyotrophic Lateral Sclerosis (ALS) or more commonly referred to as Lou Gehrig s disease Alpha motor neurons are sent more slowly 2. Disease of the myelin influences conduction speed Destroys the myelin in patches along the CNS E.g. multiple sclerosis Different types of Neurons: Differ in direction of travel: up or down 1. Motor (efferent) neurons Transmit motor commands down the spinal cord 2. Sensory (afferent) neurons Transmit signals to, and up, the spinal cord The Cerebral Cortex/ Cerebrum: Phrenology: different parts of your brain reflecting different emotions. Did so by say if someone was hit with a sword in an area in his head, and he lost his courage: that area related to courage Bogus: not true Alpha motor disease is also known as a lower motor disease Upper motor disease arises from problems in the neurons within the cortex. Occipital Lobe: The center of our visual perception Contains primary (V1) and secondary visual areas. V1: V1 is about the size of the credit card located in the back of our head. Most visual information in our eyes ends up in V1. Demonstrated phenomena known as cortical magnification Does a very simple basic property of a viewed object More neurons are devoted to center vision over peripheral Allows us to read and look in high resolution V2: V2 is responsible for binocular vision In V2 there is a class of neurons called binocular disparity neuron Very specialized neuron which allow use to preserve depth (3D) If prevented from seeing binocular vision then will not be able to see 3D

4 V3(D) and V3(V): Visual information travels through to V3(D) then travels to the parietal cortex This visual pathway supports action Visual information travels through to V3(V) to the temporal lobe This visual pathway for perception When use vision to make judgment such as that you have cup of coffee/ different colours. V4: Able to identity sim ple geometric shape Someone with a lesion to V4 may not be able to tell the difference between a triagle or square V5 (also known a MT): Able to detect movement and motion David Hubel: Worked at Harvard Recorded single cell record of V1 in the awake cat Binocular cells in V1 Blobs= color ensembles in cylindrical shapes Bloods are specialized cells used to detect orientation Interblobs= orientation sensitive Determine orientation of the object Individuals with lesion in V1 are known as cortical blindness Unable to perceive objects Nothing wrong with vision but if object is put in front of them they cannot see it. However can use vision for movement They can pick up an object without knowing there is an object in front of them. They may not actually see it but they can usually act with object even though they have no conscious awareness that they are looking at an object. Parietal Lobe: Contains primary somatosensory cortex (S1) Responsible for the planning and control of movement Interface from sensory to motor command Inferior parietal lobe (IPL) is critical for planning a movement When planning to make a movement Initial planning done in IPL Most sophisticated and recent in discovery of parietal lobe Superior parietal lobe (SPL) Online/feedback control of action: corrects movement mid movement from feedback from the environment to ensure a successful response (coffee example)

5 Lesion results in not being able to take pen Visual Spatial Neglect: High level disorder Cannot take information from a whole screen into a single image. (see up right picture) Will not notice part of page (i.e. Left side in the picture diagram) Can be treated with prison goggles o Shift vision to the left Anterior intra-parietal area (AIP): Provide our movement system to grasp When you go to grab something but in order to grasp something you must transport limb to area of object Parietal Occipital (PO): Supports transport phase of movement When need to grasp something, one must go through the PO to move limb to correct place. Temporal Lobe: Visual and haptic (touch) information mediated by structures in temporal lobe Ability to interrupt what is being said (specific to left hemisphere) Function in visual object recognition Contains primary auditory cortex Location of the hippocampus (memory and learning) Has a lot of connections with hippocampus, not part of it Play a critical role in new explicit memories o Explicitly memory: factual information o By removal of temporal and hippocampus lose complete ability for creation of long-term memories. Hippocampus and Occipital lobe work together to form these memories Can still learn new motor skills because they are learnt by cerebellum Frontal Lobe: Functions in working memory Deals with short term memories i.e. lists or number sequences Contains primary and secondary motor areas If learning new golf skill and told certain swings, for p ractice remembered by frontal lobe. Locality: drill holes into people s sides of the heads into frontal lobe: will change complete personality This is because personality and who we are is contained in frontal lobe MI: Primary motor cortex Phineas Gage Supplementary Motor Area (SMA): Premotor Area (PM) Secondary motor cortexes

6 Brainstem: Role is basic attention, arousal and consciousness. All information to and from our body passes through the brain stem on the way to or from the brain Maintain autonomic processes like heart rate Descending information must pass through brainstem to get to rest of body. Superior Colliculus (SC): responsible for making cicadae Cicadae: eye movement Cerebellum: Involved in the coordination of voluntary motor movement, balance and equilibrium and muscle tone The cerebellum is responsible formulation implicit memories (motor memory). These implicit memories are retained in cerebellum We think this because if damage to cerebellum cannot learn new skills Cerebellum ataxia: Result of lesion in cerebellum Leads to cerebellar gate o Cerebellum important for timing of movement. o In cerebellar gate cannot time muscle correctly become extremely shaky and cannot time movement. Some people have suggested that the cerebellum is an actual clock between the brain and rest of the body Some people who have stuttering may have a smart structure deficit to their cerebellum As a result, some people who stutter will have timing deficit Basal Ganglia: Group of varied origin nuclei connected to thalamus and cerebral cortex Receive and send many signals to and from the cerebral cortex (frontal lobe to be exact) Striatum receives information from cortex, output to only other basal ganglia Globus Pallidus (GPe)- receives input from the thalamus and send out inhibitor input to movement related centers. Substani Nigra (SNc)- responsible for producing dopamine Subthalamic Nuclei (SNr)- produces primary excitatory neurotransmitter in the brain Direct Pathway: (in pathway there are excitatory and inhibitory) OCD, Turets, Parkinson s linked to Basal Ganglia deficit.

7 Direct Pathway: Important part is the excitation of the Thalamus to the Cortex allowing for one to move. Goes from the Cortex to Striatium and it is excitatory Activation of the Striatium, causing inhibitory connection to GPe and GPi Those inhibitory signals to the Thalamus Inhibition of the Thalamus caused activation of the Cortex Play an important role in excitation of M1 neurons Allow primary motor cortex to become active If primary motor cortex can become active, you can move If primary motor cortex cant become active, you cant move Hemibellismus- cannot inhibit movement on one side of there body Very strong fatiguing element Parkinson s disease is a basal ganglia deficit Tremor Have extreme difficultly initiating movement o Because basal ganglia cannot activate M1. o They move very slow What is a Stroke? Importance for Our understanding of the brain? Should be known as a brain attack referring to heart attack Hemmorrhagic Stroke: Rupture of arterial wall leading to bleeding within the brain Blood very toxic to neurons Lead to neuronal death Ischemic Stroke: Blockage of artery to or within the brain Lack of oxygen (anoxia) leads to neuronal death After a stroke one will have a neural death the missing space will be filled with cerebral spinal fluid as the neurons will not regenerate this will cause a hole in the brain By finding the hole in the brain through MRI you can find out which cognitive motor tasks the individual will have problems with. Want to link structure with function.