Module 3The Brain

* The Brain

* Technology to Study the Brain

*Electroencephalograph (EEG): * records “waves” of electrical activity in the brain using metal

electrodes

*Computerized axial tomograph (CAT):* thousands of X-ray photos of the brain are combined to form a

cross-sectional picture

*Magnetic resonance imaging (MRI):* produces three-dimensional images of the brain’s soft tissues

by detecting magnetic activity from nuclear particles in brain molecules

* Technology to Study the Brain

*Positron emission tomography (PET): measures neural activity in different brain regions over several minutes by monitoring sugar glucose consumption

*Functional magnetic resonance imaging (fMRI):

measures neural activity in different brain regions averaged over seconds by monitoring blood oxygen levels

* PET Scan

* MRI Scan

*Three Major Brain Regions*Their names come from their physical location

in the human embryo.

* Hindbrain: Located above the spinal cord,

* Midbrain: Located above the hindbrain

* Forebrain: Located above the midbrain

*Development of the Brain

*Three Major Brain Regions: Hindbrain

*Hindbrain consists of:

* Medulla: controls breathing, heart rate, swallowing, digestion, and posture

* Pons: associated with sleep and arousal

* Cerebellum: regulates and coordinates body movement and may play a role in learning

*The Cerebellum

*Midbrain

Reticular formation:

* regulates and maintains consciousness

*plays an important role in controlling arousal

*Forebrain

Controls complex emotional reactions, cognitive processes, and movement patterns. Consists of: * Thalamus: the brain’s sensory relay station

* Limbic system: influences fear, aggression, and new memories

* Cerebral cortex: located on top of these structures; the most complex part of the brain

*Thalamus

*Brain’s Sensory Switchboard

*Directs incoming information from the sensory systems (except smell) to the appropriate location on the cortex.

*The Brainstem and Thalamus

*Limbic System

*a doughnut-shaped system of neural structures at the border of the brainstem and cerebral hemispheres

*associated with emotions such as fear and aggression and drives such as those for food and sex

*includes the hypothalamus, hippocampus and amygdala

*The Limbic System

*Hypothalamus

*neural structure lying below (hypo) the thalamus*directs several maintenance activities

*eating

*drinking

*body temperature

*helps govern the endocrine system via the pituitary gland*linked to emotion

*Hippocampus

*Structure linked to the processing/formation of new explicit memories

*Manufactures new neurons

*Amygdala

*two almond-shaped neural clusters that are components of the limbic system and are linked to emotion, especially rage and fear

*The Limbic System*Electrode implanted in reward center

*Main Parts of the Human Brain

*Lobes of the Cerebral Cortex

* The cerebral cortex is divided into two rounded halves, called the cerebral hemispheres.

* These hemispheres are connected together at the bottom by the corpus callosum.

* Both hemispheres are divided into four major sections called lobes:

*The Brain

*The Cerebral Cortex

Cortical Localization

*Occipital Lobes

*include the visual areas, each of which receives visual information from the opposite visual field

*Temporal Lobes

*include the auditory areas, each of which receives auditory information primarily from the opposite ear

*Visual Cortex

*Functional MRI scan of the visual cortex activated by light shown in the subject’s eyes

*Visual and Auditory Cortex

*Cortical Localization

*Frontal Lobes*involved in speaking and muscle movements and in making plans and judgments

*Parietal Lobes

*include the sensory cortex

*The Cerebral Cortex

*The Cerebral Cortex*Motor Cortex*area at the rear of the frontal lobes that controls voluntary movements

*Sensory Cortex*area at the front of the parietal lobes that registers and processes body sensations

*Association Areas*Areas of the cerebral cortex that are not involved in primary motor or sensory functions*Involved in higher mental functions such as learning, remembering, thinking, and speaking

*Cerebral Cortex - Speech

*Aphasia*impairment of language, usually caused by left

hemisphere damage either to Broca’s area (impairing speaking) or to Wernicke’s area (impairing understanding)

*Broca’s Area *an area of the frontal lobe that directs the muscle

movements involved in speech

*Wernicke’s Area *an area of the left temporal lobe involved in

language comprehension and expression

*Specialization and Integration

*Brain Activity when Hearing, Seeing &

Speaking Words

*Cortical Lateralization: Right and Left Hemispheres Function Differently

*Right hemisphere: superior to the left hemisphere in visual and spatial tasks, recognizing nonlinguistic sounds, identifying faces, and perceiving and expressing emotions

*Left hemisphere: superior to the right hemisphere at language, logic, and providing explanations for events

*Women may be more likely than men to use both hemispheres for language (their brains are more bilateralized).

*Left-Handers are Different

*65% have speech on the left (95 % RH)

*Weak correlations:

* + gifted & creative

* - reading disabilities, epilepsy, alcoholism, schizophrenia, allergies, MR

*Brain Reorganization

• Corpus Callosum– large bundle of neural fibers connecting the

two brain hemispheres and carrying messages between the hemispheres

*Brain ReorganizationCorpus Callosum

*Brain Reorganization

– Split Brain– a condition in which the two hemispheres of

the brain are isolated by cutting the connecting fibers (mainly those of the corpus callosum) between them

*Brain Reorganizati

on*The information highway

from the eyes to the brain

*Testing the Split Brain

*The Brain Can Alter Its Neural Connections

* Plasticity: the flexibility of the brain to alter its neural connections following injury

* Hemispherectomy: a radical surgical procedure in which one of the cerebral hemispheres is removed to control life-threatening epileptic seizures. The remaining healthy hemisphere takes over many of the functions of the removed hemisphere.

* Plasticity is highest in childhood, but it also occurs in older adults.

*Brain Reorganizatio

n

-- the brain’s capacity for modification as evident in brain reorganization following damage (functional plasticity) -- and in experiments on the effects of experience on brain development

*Structural Plasticity)

*Use it or Lose It

*1. Avoid Harmful Substances

*2. Exercise

*3. Eat Sensibly

*4. Challenge Yourself Mentally

*5. Wear Your Helmet/Seat Belt.

*Blood-Brain Barrier

* Beneficial substances allowed to enter the brain through the blood-brain barrier are blood gases, such as oxygen, and small nutritional molecules.

* An important nutritional molecule transported out of the bloodstream in this way is glucose.

* Scientists have learned how to trick the blood-brain barrier into accepting therapeutic drugs through the bloodstream to the brain.

*Blood-Brain Barrier