Module 4: The Brain

Why study the brain? Every good thing happens in the brain Thoughts, memories, dreams, pleasure, love, decisions, motivation Everything that we want to avoid happens in the brain Anger, nightmares, physical pain, emotional pain, anxiety, depression “The mind is what the brain does” So is an emotion So is a behavior

How do we study the brain? Autopsies Clinical observations EEG Neuroimaging

Electroencephalogram (EEG) an amplified recording of the waves of electrical activity these waves are measured by electrodes placed on the scalp

Neuroimaging PET (positron emission tomography) Scan Radioactive form of sugar is given Sugar goes to the region of the brain that is active MRI (magnetic resonance imaging) uses magnetic fields and radio waves Generates images that distinguish among different types of soft tissue Functional MRI Reveals blood flow, therefore brain activity Compares successive MRI scans while the patient is performing a task

MRI Schizophrenia

fMRI The visual cortex is activated as the subject looks at faces

The Older and Newer Brain Structures

Older Brain Structures: The brainstem Relays sensory input except smell Filters information Controls alertness Brainstem is the medulla and the pons Brainstem is the crossover point – nerves from each side of the body connects to the opposite side of the brain. Pons Coordinates movements Heartbeat and breathing Brainstem

Cerebellum the “little brain” at the rear of the brainstem Non-verbal learning: judge time, modulate emotions, discriminate using senses helps coordinate voluntary movement and balance Baseball sized Clearly works with the pons Damage results in difficulty walking, keeping balance, shaking hands, etc. jerky-exaggerated movement

The Limbic System Hippocampus: processes memory Amygdala: Influences aggression and fear Perception of these emotions Processing of emotional memories Hypothalamus: Monitors the blood chemistry and the pituitary gland Influences feelings of hunger, thirst, body temperature and sexual arousal Houses the pleasure or reward centers Limbic system resides around the older brain parts and the cerebral hemispheres If hippocampus is damaged, individuals become unable to process new memories Amygdala has two bean sized structures It is likely that addictive behaviors are partly due to damage or malfunction of the limbic system Note that pleasure is associated with neurotransmitters endorphines and dopamine

The Cerebral Cortex: our resource for adaptability Cerebral Hemispheres Corpus Callosum the intricate fabric of interconnected neural cells that covers the cerebral hemispheres the body’s ultimate control and information processing center Corpus callosum maintains the information flow between the two hemispheres of the brain

The Structure of the Cortex Frontal Lobes: Thinking, planning, movement Parietal Lobes: body sensation Occipital Lobes: Vision Temporal Lobes: Hearing, language Lobes are separated by prominent fissures (folds) 80% of the weight of the brain is the cortex It has 300 trillion synaptic connections

The Motor Functions Parts of the body requiring precise control takes up more room on the motor cortex

Sensory functions Higher sensitivity in an area is associated with larger area on the sensory cortex Lips in humans Whiskers in rats Stimulation in the sensory cortex produces feelings Stimulation of the auditory cortex  hearing sounds (hallucinations)

Association areas of the cortex: the Case of Phineas Gage Gage was a railroad construction foreman An 1848 explosion forced a steel tamping rod through his head Others said he was “…no longer Gage…” Lost his job, worked as a sideshow exhibit

Language functions: mostly on the left hemisphere Some individuals have discrepant abilities to read-write-speak-sing. READING Register in visual area Transform words into auditory code Auditory code received and understood Motor area produces the word

Brain Plasticity The brain’s capacity for modification Brain reorganizes itself following damage (especially in children) Brain reorganizes itself through intense learning experiences London cab drivers

Our divided brain Hemispheres control and receive information from the opposite sides of the body Hemispheric Specialization Left hemisphere: language, logic, and complex motor behavior Right hemisphere: non-linguistic functions including recognition of faces, places, and sounds (music) The hemispheric specializations are evident from studies of Damage to one hemisphere (I.e. Broca’s area) Split-brain subjects