Higher Mental Functions

Anatomy and Physiology II

BIO 232

Cerebral Cortex

• Frontal

• Voluntary control of muscles, planning, decision making, personality & higher intellectual processes

• Parietal

• Cutaneous & muscular sense, speech, interpretation of textures and shapes

Cerebral Cortex

• Temporal

• Auditory sensations, memory management

• Occipital

• Visual processes & eye movements

• Deep Insula

• Memory & integration of cerebral activities

The Electroencephalogram

• Summed activity of millions of nerve cells

• Not APs but synaptic potentials

• Recorded from the surface of the scalp - surface electrodes

The EEG - Wave Types

• Alpha - Parietal & occipital

• 9-12 Hz

• Beta - Frontal

• 13-25 Hz

• Theta - Temporal & Parietal

• 5- 8 Hz

• Delta - Over entire cortex

• 1- 5 Hz

Sleep

• Recurring process

• Newborns - polyphasic

• Children - biphasic

• Adults- monophasic

• Circadian cycle

Slow Wave Sleep

• Four stages

• Progressively slower EEG frequency

• Progressively higher EEG voltage

• Over 30-45 min

Slow Wave Sleep - Physiological Changes

• Muscles relaxed

• Postural adjustment - (5-20 min)

• Parasympathetic outflow dominates

• Heart rate down

• Blood pressure down

• Respiration rate down & becomes more shallow

• GI motility up

Sleep with Rapid Eye Movements

• Second state of sleep

• 90 min after onset of sleep - tonic physiological measure change

• EEG desynchronized

• Brain temperature rises

Sleep with Rapid Eye Movements

• Sympathetic activation

• Heart rate up

• Blood pressure up

• Respiration rate up & more irregular

• General head neck & body musculature actively inhibited

• Only eye & middle ear muscles active

Sleep with Rapid Eye Movements

• Phasic events

• Rapid eye movements

• Middle ear muscle are phasically active

• If REM is interrupted

• Large % report - dreaming

• 74-95%

Typical Nights Sleep

Localization of Higher Functions

• Does not mean that a specific function is exclusively mediated by only one brain region

• Rather - these areas are more concerned with one set of functions than with others

• Since most higher functions require the integrated activity of several brain areas

Association Cortex

• Increases in size through phylogeny - greatest extent in humans

• Prefrontal cortex

• Certain spatial learning tasks (maze)

• Lesion around the sulcus principalis

• Emotional responsiveness

• Lesion medial orbital cortex

• Reduced rage & anger responses in primates

Association Areas of Temporal Cortex

• Memory function

• Lesion inferior temporal cortex

• Deficits in the rate of learning visual tasks

• Lesion superior temporal cortex

• Deficits in the rates of learning auditory patterns

• No deafness

Localization of Language

• 1860’s - Paul Broca - French neurologist

• Pointed out that damage to a particular area of the cortex produced a speech disorder - aphasia

• Damage was on the sides of the frontal lobes - Broca’s Area

• Damage to the left - aphasia

• Damage to the right - no problem

• True of 95% of the patients

Localization of Language

• German neurologist - Carl Wernicke

• Second type of aphasia

• Damage to another site of the left hemisphere

• Temporal lobe - Wernicke’s Area

• Lies between the primary auditory cortex & angular gyrus

• Broca’s & Wernicke’s area connected by arcuate fasciculus

Broca’s Area

• Speech is labored & slow and articulation is impaired

• Answer to a question will make sense but can’t be expressed in a fully formed gram- matically correct sentence

• Same errors are made in writing

Wernicke’s Aphasia

• Speech is phonetically & even grammatically normal but it is semantically deviant

• Words are often strung together with considerable facility, even appropriate voice inflections - has recognizable structure of a sentence

• However the words chosen are often inappropriate & sometimes nonsensical

Wernicke Model of Speech Production

• Underlying structure of a word - Wernicke’s area

• Next passed to Broca’s area

• In Broca’s area - detailed motor program for vocalization produced

• Next passed to adjacent area of the motor cortex

Prosophenosia

• Failure to recognize familiar faces

• Highly specific disorder

• All mental tasks including visual processing can easily be performed

• However can not recognize the face or picture of the face of a familiar person

Prosophenosia

• Identity of familiar person is not lost - since if that person speaks - recognition

• Lesion stereotyped

• Undersides of both occipital lobes - extending forward to the inner surface of the temporal lobes

• In monkey, neurons have been found that respond to specific features of a monkeys face

Memory

• The storage and retrieval of information

• Memory storage occurs in stages and is continually changing

• The hippocampus and adjacent areas are in involved in memory processes

• Memory traces (chemical and structural changes that encode memory) are widely distributed

Stages of Memory

• Short Term Memory (STM) - Working memory

• Lasting for seconds - preliminary step for long term memory

• Capacity - limited to 7 to 8 chunks of information such as digits or sequence of words in an elaborate sentence

Stages of Memory

• Long Term Memory (LTM)

• Limitless capacity

• Ability to retrieve declines with aging

• Thus log term memories can be forgotten

• Our memory bank is continually changing with time

Transfer from STM to LTM

• Emotional state - learn best when alert, motivated and aroused

• Shocking events are almost immediately transferred to LTM

• NE involved - more released when we are excited

• Rehearsal - opportunity to rehearse or repeat material enhances memory

Transfer from STM to LTM

• Association of new information with “old” already stored in LTM

• Automatic memory - not all information that becomes LTM reaches consciousness

• e.g. when concentrating on what someone is saying you may also form automatic memory of any annoying habits or gestures or favorite phrases

• Memories placed into LTM take time to become permanent - memory consolidation

Categories of Memory

• Fact (declarative) memory - involves placing explicit information such as names, faces, words and dates into storage

• When theses facts are stored the context in which they are learned is also stored - The pretty/handsome new face is associated with the Friday night dance.

• Skill (procedural) memory - less conscious learning - usually involves motor activities

• Acquired only through practice - like learning to ride a bike or play the piano

• Typically do not preserve the circumstances of learning - best remembered in the doing

Brain Structures Involved in Memory