NEUR 2.1 - Anatomy of Brain Function

• Frontal Lobe

   

  Primary Motor Cortex

  • Premotor cortex: motor planning

   

  • Primary motor cortex: execution

   

   

  Speech production (Broca's Area)

   

  • Compulsive-obsessive behaviours come with lack of inhibitory control
• Frontal Lobe functions

  Last place where neurons fire their signals - go down spinal cord and cause spinal contraction (all voluntary movement)

   

  • Any damage = paralysis in part of body 

  Executive Functions:

  • Reasoning, planning, problem-solving
  • Inhibitory control (regulation of appropriate behaviour - select + inhibit)
  • Working memory

   

   

  Motor Functions 
• Frontal Lobe Injury - Broca's Area

  Left frontal lobe

  
  

  Broca's Aphasia

  • Spontaneously speaking = slow and non-fluent
  • Anomia: difficulty finding appropriate words
  • Repeating

  However:

  • Comprehension mostly UNAFFECTED
  • Speech still carries meaning

  Phineas Gage

  • Short of temper, engaging in inappropriate behaviour = lack of inhibitory control
• Parietal Lobe

  (Major volume of human brain)

   

  • Runs down centre of brain, up spinal cord 

  Primary Somatosensory Cortex

  • Perception of touch

   

  Links vision with action
• Parietal Lobe Functions

  Sense of space and locations

  • Gives sense of stable world around us relative to our body position

   

   

  Spatial Attention

  • Directing attention and eye movements to explore visual world

   

   

  Linking vision to action

  • Represents spatial location of objects around us for guiding actions
• Parietal Lobe Injury

  Any damage to neurons = lose sense of touch (numbness)
• Occipital Lobe

  Input from retina in the eyes goes first to the back of the brain into --> primary visual cortex
• Occipital Lobe Functions

   

  Posterior part of the brain (inferior to Parietal Lobe)

   

  Primary Visual Cortex (V1)

  • All visual perception

   

   

  Higher visual areas

  • Different regions process shape, colour, orientation, motion

  (being able to identify objects separate from its background)

   
• Temporal Lobe

  Purpose: Language and ability to process speech

   

  Cortex: Primary Auditory Cortex

   

  Injury: Language comprehension

  (Wernicke's Area)
• Temporal Lobe Functions

   

  Primary Auditory Cortex

  • Perception of sound

   

  Language comprehension

  (Wernicke's Area)

   

   

  Medial Temporal Lobe:

  • Limbic System

  Amygdala and hippocampus (more details)
• 
  

  Left posterior temporal lobe

  
  

  • Lesions lead to deficits in language comprehension 
  • Carry no meaning - deficit in connecting meaning and understanding others' language

  
  

  However:

  • Patients are able to speak fluently with normal prosody: rhythm, intonation
• Left Hemisphere Injuries to the Brain

  Broca's (left frontal lobe) & Wernicke's (left posterior temporal lobe)
• Limbic System


  Area: Medial Temporal Lobe

  PURPOSE: involved in behavioural and emotional responses - EG: feeding, reproduction, caring for young, fight/flight response
• Amygdala 


  Fear and arousal

  • Responds to threats / danger
  • Fear / learning phobias
  • EG: alerting (MRI scanning showing scary things = amygdala rapidly becoming highly active
• Hippocampus 


  Learning and memory

  • Forming new episodic memories
  • Damage causes = anterograde amnesia: can't form new memories of events
• Corpus Callosum

  PURPOSE: interconnects and allows communication between both hemispheres

   

  "Split-brain" patients have left and right hemispheres disconnected = 2 hemispheres cannot communicate with each other
• Homunculus

  Primary Sensory Cortex and Primary Motor Cortex

   

  • Brain stimulation leads to sensation or movement (brain twitch)
  • Size of area on cortex represents sensitivity or fine motor control

  EG: more sensitive areas like lips and mouth = more representative on sensory cortex
• The Brainstem connections

  • cerebral hemispheres + the spinal cord
  • carries information between the cerebral hemispheres and the cerebellum +the cerebellum and the spinal cord
• Autonomic Nervous System

  
  

  2 divisions:

  • Sympathetic Nervous System
  • Parasympathetic Nervous System
• ANS: Sympathetic Nervous System

  
  

  • Emotional arousal, stress, fear
  • "fight-or-flight" response
  • Increases heart rate, respiration, perspiration, pupils dilate
• ANS: Parasympathetic Nervous System


  • "Rest and Digest"
  • Lowers heart rate, respiration
  • Increases stomach, intestine activity (digestion)
  • "opposes" the sympathetic nervous system
• The Brainstem: Medulla

  Main centre for Autonomic Nervous System functions

  • Controls heart rate, respiration, regulation of blood pressure, body temperature
  • Reflex centres for coughing, sneezing, swallowing, vomiting

  EG: Keep boding alive in changing environments (homeostasis) - in cold weather, small muscles around the blood vessels that go to extremities to the hands and feet, contract and restrict blood flow out to the extremities = keeps blood central in our core to keep main organs warm
• Disorders of Consciousness: Persistent Vegetative State

  Patients have no conscious awareness

  • Severe damage to upper brain (hemispheres + cortex)
  • If brainstem is not damaged = autonomic nervous system functions the same
  • Sometimes normal respiration, control of heart rate, some face and eye movements remain (through cranial nerves)

   

   
• Amyotrophic Lateral Sclerosis (ALS) or Motor Neuron Disease


  Disorder of consciousness with progressive loss of ability to control muscle contractions/movements - 'locked in syndrome'
• ALS/Motor Neuron Disease

  • Loss of motor neurons to spinal cord
  • Intact cerebellum and brainstem, but "disconnected" from spinal cord
  • Normal cognitive function, vision, and hearing, but patients cannot move
  • Loss the output of the brain from motor cortex down the spinal cord for muscle contraction and movement
• Persistent Vegetative State

  Patients appear the same as those with ALS/Motor Neuron Disease, however cortex is fully functioning in ALS/Motor Neuron Disease patients
• Detecting brain activity and communication in ALS/Motor Neuron Disease patients


  1. Functional MRI used

  2. Allows patients to communicate by "imagine playing tennis", "imaging walking around your house"
• ALS/Motor Neuron Disease patients may have conscious experience and intentions
• Low - to - high level functions

  LOW: BRAINSTEM

  • Autonomic Nervous System functions (heart rate, respiration, blood pressure, homeostasis)

  HIGH: CEREBRAL HEMISPHERES - CORTEX

  • Frontal Lobe (planning, reasoning, problem solving)
  • Language + perception
• Summary of the Cerebellum

  • Hind brain
  • Sense of balance and coordination of complex movement
  • Motor learning - fine adjustment of movement based on feedback

   

  Very important for the automatic things we do

  EG: balance by standing on 2 feet, constantly making adjustments using changes in muscles along our spine and core that keeps our centre of mass balanced over our feet - all handled automatically by cerebellum and by feedback loops 
• Primary Motor and Sensory Areas

  
  

  PRIMARY MOTOR CORTEX ACTIVITY = movement (muscle contraction)

  • Send signals directly down spinal cord for muscle contraction and movement

  EG: Analogy - sequential series of commands for muscle contractions

  
  

  Brain retrieves program for learnt skilled actions - EG: signature, tennis swing

  
  

  
  

  PRIMARY SENSORY CORTEX ACTIVITY = sensation

  • receiving signals back through the spinal cord for our sense of touch
• 
  

  The control and coordination of skilled movement relies on feedback circuits between the motor cortex (sending signals down the spinal cord causing muscle contraction), muscle movement, and sensory info that comes from back from senses into our brain
• WHEN FEEDBACK MATCHES PREDICTIONS FROM PLANNED ACTIONS

   

  = sense of agency

  • Brain automatically links sensory events and own actions to infer causality
  • Sense that my action caused event
• Feedback Cycles

  Movement relies on a feedback cycle between the plans for action and the sensation from action.

  Movement relies on a feedback cycle between the sensory predictions from motor programs and sensory feedback.