3 Cerebral Cortex and Diencephalon

Association

Connects with different parts of the brain in the same hemisphere

Commissural

Runs between hemispheres; Ex. corpus callosum

Projection fibers

Connect cortex with different parts of the CNS; Ex. internal capsule

Frontal lobe

Has 2 main functions:

• Controlling voluntary mvmt

• Thinking/problem solving

Primary Motor Cortex

 Located on precentral gyrus

 Control voluntary movements on the contralateral side

 Related tracts: corticospinal and corticobulbar

 Lesion: Paralysis on the contralateral side of the body and muscles of facial expression on the bottom portion of the face

Premotor Cortex

 Located just anterior to primary motor cortex

 Control action of trunk and limb muscles

 “Body part ownership”

 Related tracts: reticulospinal and vestibulospinal

 Lesion: Unilateral neglect

Supplementary Motor Area

 Located medial to the premotor cortex

 Stores motor memories, directs activity of the primary motor cortex

 Lesion: Apraxia, motor planning deficit

Broca’s Area

 For most people located in the left hemisphere only. (Left-handed people may have a right Broca’s area).

 Contains motor programs for speech and language

 Note: In non-dominant hemisphere, corresponding area controls nonverbal communication

KNOW THE AREA IN/ON THE BRAIN FOR PRACTICAL

Ataxia

• Uncoordinated movement that manifests when voluntary movements are attempted; may influence gait, posture and patterns of movement.

• Often related to cerebellar lesion

Apraxia

 An impairment of voluntary learned movement that is characterized by an inability to perform purposeful movements not accounted for by inadequate strength, loss of coordination, impaired sensation, attention deficits or lack of comprehension

 Often related to lesion in the supplemental motor area of the cortex

Orbitofrontal Cortex

 Contains areas for impulse control, inhibition of inappropriate behaviors and carrying out plans

 Lesion: Patient can’t make realistic plans, or carry out plans they make. Tend to have trouble with focus, organization and inhibition of impulses (prefrontal syndrome)

The right side of the brain control left side movements.

True

Ventromedial Frontal Cortex

 Part of limbic system

 Connects emotions with thought, attaches emotional meaning to life experiences

 Lesion: Flat emotional affect

 Underactive in people with depression and overactive in people with mania

Anterior Cingulate

 Part of limbic system

 Helps integrate thought, motivation, attention and behavior

 Allows a person to “tune” into their own thoughts

Expressive aphasia

• Pt can understand speech but cannot produce speech to respond

• Damage to the Broca’s area

Parietal lobe

Involved in perception and processing of sensation

Somtasensory Cortex

 Located on the postcentral gyrus

 Perceives sensations such as pain, temperature, pressure, touch, vibration and proprioception

Somatosensory Association Area

 Responsible for interpretation of somatosensory information

 Stereognosis – the ability of someone to recognize an object by touching it.

 Disorders of body image, such as anorexia nervosa and unilateral neglect, are linked to dysfunction in this area

Parietotemporal Association Cortex

Abstract thought, reasoning, reading and writing, mathematics and spatial perception

Angular Gyrus

Understanding written language

Occipital lobe

Visual perception

Primary Visual Cortex

 Visual perception

 Lesion: Loss of vision in the opposite visual field ( hemianopsia)

Visual Association Cortex

 Located anterior to primary visual cortex

 Interpreting visual stimuli

 Lesion: Patient can see objects or faces, but not recognize (visual agnosia)

Temporal Lobe

Contains portions of the limbic system (emotion, memory), auditory system, olfactory system, area for recognizing faces

Primary Auditory Cortex

 Sound is perceived

 Auditory cortex on each side get input from both ears

Auditory Association Cortex

 Located posterior to the primary auditory cortex

 Responsible for interpretation and understanding of sounds

Wernicke’s Area

 Understanding language (verbal, sign and written)

 Usually located only on left side

 Lesion: Receptive aphasia

Receptive Aphasia

 Unable to understand any form of language

 Can speak fluidly, but what they say doesn’t make sense

Global Aphasia

Expressive + receptive aphasia

Inferotemporal Lobe

 Recognition of faces, objects, colors

 Lesion: Patients can’t recognize faces of people they know (prosopagnosia).

 Prosopagnosia is an early sign of Alzheimer’s disease

Olfactory Cortex

 On the medial part of the temporal lobe

 Responsible for perceiving odor

 Lesion: Loss of sense of smell (anosmia)

Amygdala

 Medial side of temporal lobe

 Involved in strong negative emotion

 Connections to the hypothalamus

Hippocampus

 Medial side of temporal lobe

 Involved in creation of new long-term memories

 Lesion: If lesion is (B) patient will not be able to create new long-term memories and have anterograde amnesia

 Can generate new neurons throughout life

Diencephalon

• Located just above the brainstem

• Has 4 components:

  • Thalamus

  • Hypothalamus

  • Epithalamus

  • Subthalamus

Thalamus

 Right and left thalami are located on either side of the 3rd ventricle

 Almost all information that reaches the cortex passes through thalamus first

 Ex: Pain, temperature, pressure, touch, auditory, visual taste and vestibular sensations synapse in thalamus before cortex

Relay Nuclei

6 receive info from a specific area of the nervous system and send the info to the cerebral cortex:

 2 general sensory (receive from contralateral side of body)

 2 special sensory (visual and auditory)

 2 motor

Association Nuclei

 Receive action potentials from CNS

 Send projections to limbic regions of the cortex where they connect sensory input to emotional responses

 Example: Fear aroused with a particular touch or smell

Intralaminar Nuclei

 Have reciprocal connections with the basal ganglia and the limbic system

 Send projections to area of the cortex. Many interconnections

 Involved in maintaining conscious awareness

 Lesions may cause a coma

Reticular Nucleus of Thalamus

 Narrow band of cells anterior and lateral to the thalamus

 Function is to determine which signals will be conveyed to the cerebral cortex

 Controls the activity of the relay nuclei

*There is evidence that dysfunction of the reticular nucleus is linked to disorders such as autism in which the ability to modulate sensory input is limited

Thalamic Syndrome

 Typically due to compromise of blood supply from the posterior cerebral artery

 Symptoms: hemianesthesia, sensory ataxia (motor incoordination due to loss of proprioceptive information from muscles, joints and tendons) and thalamic pain

 Thalamic pain – intense and unpleasant. Is often not treated effectively with pain medications. Caused by abnormal pain modulation when the thalamus is damaged

 Also called central pain syndrome

Hypothalamus

 Located anterior and inferior to the thalamus

 Controls the autonomic nervous system

 Regulates activity of endocrine glands

 Connects physiological responses to emotions

 Regulates water balance, hunger, thirst, sexual drive, body temperature, sleep/wake cycles

What are the hormones that are released in the hypothalamus?

• Vasopressin

• Oxytocin

Vasopressin

Controls water balance; causes constriction of

blood vessels -> increase BP

Oxytocin

Causes constriction of smooth muscles in uterus and mammary glands

Central Autonomic Fibers

 Neurons that descend directly from hypothalamus to the brainstem and spinal cord in the reticulospinal tracts

 These fibers synapse onto sympathetic and parasympathetic neurons and control the function of visceral organs.

 Hypothalamus controls blood pressure, blood flow and other physiological functions

Pituitary Gland (Hypophysis)

 Hypothalamus controls the hypophysis (pituitary gland)

 Located just below the hypothalamus

 Has an anterior lobe and posterior lobe

*Affects many areas of the body

Epithalamus

 Consists of pineal gland and other small nuclei

 Secretes hormone called melatonin

Subthalamus

 Contains subthalamic nucleus (Part of basal ganglia circuitry)