Introduction to Neuroscience - Presentation 4 (1).pdf

Introduction to Neuroscience Presentation 4 - Prof. Boaz Barak Brain development Babies are born with millions of neurons Neurons are connected by synapses, which allow information to pass from one neuron to another From birth onwards experiences and interactions help to build syn...

Introduction to Neuroscience Presentation 4 - Prof. Boaz Barak Brain development Babies are born with millions of neurons Neurons are connected by synapses, which allow information to pass from one neuron to another From birth onwards experiences and interactions help to build synaptic connections By the age of two a child's brain has developed more synapses than are needed Synapses that are used are strengthened, while those that are not used are discarded – we ‘use it or lose it’ This is called 'pruning' 2 Sensitive and critical periods The brain is genetically predisposed to expect certain experiences The more a child is exposed to these experiences the stronger the connections ‘Sensitive periods’ are when brain development is more strongly affected by experiences A 'critical period‘ refers to the irreversible impact of experience on development. There is some evidence of windows of opportunity closing, but overall the brain retains remarkable plasticity 3 The Brain and Maltreatment Infants need a relationship with a consistent, https://www.youtube.com/w emotionally available caregiver atch?v=VNNsN9IJkws The presence or absence of sensitive care has an impact on the infant's stress response and brain development The majority of changes to the brain following abuse and neglect are adaptations to adverse environments rather than irreparable damage 4 Nervous System Organization (Cont.) ©John Wiley & Sons, Inc. 2008 Carpenter/Huffman: Visualizing Psychology  How do we move? talks talk Brain Muscles  Motor control systems in the cortex Primary motor cortex – source of pyramidal tract neurons Supplementary motor cortex - conception and initiation of movement. - lesions cause deficits in voluntary movement or speech Premotor cortex - important in motor coordination. - lesions cause impairments in stability of stance, gait and hand coordination https://www.youtube.com/watch?v=APuiZCxDnTA  Motor control systems outside the cortex Cerebellum -controls neural ‘programs’ for the execution of skilled movements Basal ganglia - a group of subcortical forebrain nuclei (caudate nucleus, putamen (= striatum), globus palludus, subthalamic nucleus) - modulate patterns of motor activity  The flow of information Information from the motor cortex goes to the spinal cord and to the muscles Corticospinal Tracts (are also called pyramidal tracts Spinal Cord Spinal Segments Section of the Spinal Cord Types of Motor Neurons Synapses with peripheral motor neurons Neuro-Muscular Junction (NMJ) Synaptic transmission from the nerve to the muscle The right side of our brain moves the left side of our body and vice versa https://www.youtube.com/watch?v=zxpbgiVko-1  Section of the spinal cord Spinal cord consists of gray matter and white matter: – Gray matter: It lies in the center and forms projections called horns. Anterior horn contains motor neurons and posterior horn contains sensory neurons – White matter: It lies outside and consists of various tracts. The main motor tracts are the lateral corticospinal tracts in lateral column  Spinal reflexes The knee stretch reflex Mediated at the level of the spinal cord Do not require any cortical input Sensory neuron synapses directly to motor neurone Muscle contracts to cause limb extension  The homunculus The part of the brain that makes us move is our motor cortex The homunculus show how our body is represented within our brain Motor disorders Stroke and hemiplegia  Parkinson’s disease Resting tremor in limbs – disappears on movement or during sleep Muscle rigidity – resistance to passive movement: jerky (cogwheel) movement Akinesia – lost ability to move muscles Altered cognitive function, depression and/or dementia Deficits in movement controlled by extra-pyramidal motor pathways  Neuropathology of Parkinson’s disease Loss of dopaminergic neurons in the substantia nigra Nigro-striatal pathway degeneration Leading to a depletion of striatal dopamine Some degeneration of other dopamine pathways too Dopamine Glutamate X Striatum GABA  Parkinson’s disease neurological conditions Normal Parkinson’s condition disease Inhibitory connections: gray and black arrows Excitatory connections, as pink and red Degeneration of the dopamine pathway in Parkinson ’ s disease leads to differential changes in activity in two projections, indicated by changes in the darkness of the connecting arrows (darker arrows indicate increased neuronal activity and lighter arrows, decreased activity) Basal ganglia inhibitory output to the thalamus is increased in Parkinson’s disease.  Parkinson’s disease – drug therapies Prior to 1960s there were no effective treatments Dopamine involvement in PD -> drugs which increase brain dopamine Dopamine itself cannot cross from the blood to the brain Dopamine precursor, L-DOPA, can enter the brain Converted there into dopamine https://www.youtube.com/watch?v=dwu17GTKihA  Parkinson’s disease – DBS https://www.youtube.com/watch?v=wZZ4Vf3HinA THE SENSORY SYSTEM It is part of the nervous system that consists of: Sensory receptors (receive stimuli from the external and internal environment). Neural pathway (conduct information from the receptors to the brain). Parts of the brain (deals with processing the information). How do we see?  The Visual Sense Light – consists of quanta (photons) that vibrate at a particular range in the electromagnetic spectrum  The Eye Pupil  light enters the eye through the pupil Iris  dilates or constricts to vary the amount of light entering the eye Lens  clear, elastic structure that can change its shape to focus an image on the retina Retina  back layer of the eye that contains visual receptor cells  The Retina Visual Receptor Cells – Called photoreceptors these are the rods and cones – Rods  very sensitive to light and enable us to see at night – Cones  specialized for bright light conditions and enable us to see close and fine detail How does information from your eye get to your brain?  Human Visual System Exposure Image formation Detection Processing Control Cornea Iris/pupil Retina Brain Lens Photoreceptor Rods sensitivity Cones How do we hear? The anatomy of audition How do we sense?  Touch The Spinal cord – Spinal segments (30)- spinal nerves within 4 divisions of spinal cord.  Touch Somatosensory Cortex – Cortical Somatotopy: Homunculus