The Brain Copyright 2010 Pearson Education Inc Copyright

Cerebral Hemispheres How is the brain organized? – Define the major lobes – Distinguish between gyri and sulci – Compare the functional areas of the cerebral cortex Copyright © 2010 Pearson Education, Inc.

The cerebrum is divided into three major areas: • Cerebral Cortex • Internal White

The cerebral hemispheres form the superior part of the brain. It makes up most

A. The Cerebral Cortex The cortex is composed of gray matter which contains neuron cell bodies, dendrites, glial cells and blood vessels. It is only 2 to 4 mm in thickness. The folds increase the surface area. Copyright © 2010 Pearson Education, Inc.

The surface of the hemispheres is marked by elevated ridges called gyri and shallow

Lissencephaly, which literally means smooth brain, is a rare brain formation disorder caused by defective neuronal migration during the 12 th to 24 th weeks of gestation resulting in a lack of development of brain folds (gyri) and grooves (sulci). Copyright © 2010 Pearson Education, Inc.

Normal Brain Copyright © 2010 Pearson Education, Inc. Lissencephaly

Lissencephaly Copyright © 2010 Pearson Education, Inc. Normal Brain

The prognosis for children with lissencephaly varies depending on the malformation. Many individuals remain in a 3 -5 month developmental level, while others may appear to have near normal intelligence and development. Some children with lissencephaly will be able to roll over, sit, reach for objects, and smile socially. Copyright © 2010 Pearson Education, Inc.

The cortex contains three kinds of functional areas: – Motor area – Sensory areas

Each hemisphere is primarily concerned with sensory and motor function on the opposite (contralateral)

Each hemisphere is not equal in function. There is lateralization (specialization) of cortical functions. Left hemisphere is logical while the right is creative Copyright © 2010 Pearson Education, Inc.

The motor areas control voluntary movement and are found primarily in the posterior part of the frontal lobes and include: – the primary motor cortex, – premotor cortex, – Broca’s area and – the frontal eye field. Copyright © 2010 Pearson Education, Inc.

Figure 12. 8 a Functional and structural areas of the cerebral cortex. Motor areas Central sulcus Primary motor cortex Premotor cortex Frontal eye field Broca’s area (outlined by dashes) Prefrontal cortex Working memory for spatial tasks Executive area for task management Working memory for object-recall tasks Solving complex, multitask problems (a) Lateral view, left cerebral hemisphere Motor association cortex Primary sensory cortex Primary motor cortex Sensory association cortex Multimodal association cortex Copyright © 2010 Pearson Education, Inc. Sensory areas and related association areas Primary somatosensory cortex Somatic Somatosensory sensation association cortex Gustatory cortex (in insula) Taste Wernicke’s area (outlined by dashes) Primary visual cortex Visual association area Auditory association area Primary auditory cortex Vision Hearing

Primary motor cortex is located in the precentral gyrus of the frontal lobe. Their function is to control the precise voluntary movements of the skeletal muscles. Copyright © 2010 Pearson Education, Inc.

Figure 12. 9 Body maps in the primary motor cortex and somatosensory cortex of the cerebrum. Posterior Motor Sensory Anterior Motor map in precentral gyrus Sensory map in postcentral gyrus Toes Genitals Jaw Tongue Swallowing Copyright © 2010 Pearson Education, Inc. Primary motor cortex (precentral gyrus) Primary somatosensory cortex (postcentral gyrus) Intraabdominal

Common disorders include stroke, tumors or traumatic brain injury. Effects include loss of specific

Premotor cortex is located just anterior precentral gyrus of the frontal lobe. It's function is to control learned motor skills of a repetitive or patterned nature, for example typing. Copyright © 2010 Pearson Education, Inc.

Disorders of the premotor cortex are commonly due to stroke, tumors or trauma. One condition is known as Apraxia or the inability to recognize objects by touch. Copyright © 2010 Pearson Education, Inc.

Broca’s Area lies anterior and inferior to the premotor cortex. It is typically found

Aphasia is a disorder caused by damage to the parts of the brain that control language. It can make it hard for you to read, write, and say what you mean to say. Copyright © 2010 Pearson Education, Inc.

There are four main types: • Expressive aphasia - you know what you want

There are four main types: • Expressive aphasia • Receptive aphasia - you hear

There are four main types: • Expressive aphasia • Receptive aphasia • Anomic aphasia • Global aphasia - you can't speak, understand speech, read, or write Aphasia Copyright © 2010 Pearson Education, Inc.

Frontal eye field is located on or near the premotor cortex and is above

The sensory area of the cerebral cortex is concerned with conscious awareness. Areas involved with this function are found in the parietal, temporal and occipital lobes. Copyright © 2010 Pearson Education, Inc.

Primary somatosensory cortex receive information from the sensory receptors in the skin and proprioceptors (position receptors) in the skeletal muscles, joints and tendons. Copyright © 2010 Pearson Education, Inc.

Figure 12. 9 Body maps in the primary motor cortex and somatosensory cortex of the cerebrum. Posterior Motor Sensory Anterior Motor map in precentral gyrus Sensory map in postcentral gyrus Toes Genitals Jaw Tongue Swallowing Copyright © 2010 Pearson Education, Inc. Primary motor cortex (precentral gyrus) Primary somatosensory cortex (postcentral gyrus) Intraabdominal

• Somatosensory association cortex serves to integrate sensory information such as temperature, pressure

Association Areas Multimodal association areas receive input from multiple senses and sends outputs to multiple areas. There are 3 main areas: • Anterior association area • Posterior association area • Limbic association area Copyright © 2010 Pearson Education, Inc.

Anterior association area Is located in the frontal lobe. It is considered the most complicated and is involved with learning (cognition), recall and personality. Additional functions include working memory, abstraction and planning. Copyright © 2010 Pearson Education, Inc.

Posterior association area Covers the temporal, parietal and occipital lobes. This area is involved with pattern recognition. It is what allows us to recognize familiar places. An additional function understands of written and spoken language. Copyright © 2010 Pearson Education, Inc.

Isolated problems with these association areas are rare. Trauma or stroke often leads to

Limbic association area This area is sometimes called the pleasure center. In animal studies it is correlated with sexual arousal, behavior and olfaction (think about this last one). Big Bang Copyright © 2010 Pearson Education, Inc.

B. Cerebral White Matter The cerebral white matter is responsible for communicating between the cerebral areas and the lower CNS centers. This area consists largely of myelinated fibers bundled into large tracts. Copyright © 2010 Pearson Education, Inc.

The white fibers or tracts are classified based on which direction they run. – Commissural fibers connect gray areas of the two hemispheres allowing them to coordinate. – Association fibers connect different parts of the same hemisphere – Projection fibers either enter the cerebral cortex from the lower brain or descend to the lower areas from the cortex. Copyright © 2010 Pearson Education, Inc.

Corpus Callosum (Commissures) Copyright © 2010 Pearson Education, Inc.

Association Fibers Copyright © 2010 Pearson Education, Inc.

Figure 12. 10 Types of fiber tracts in white matter. Longitudinal fissure Lateral ventricle Basal nuclei • Caudate • Putamen • Globus pallidus Thalamus Superior Association fibers Commissural fibers (corpus callosum) Corona radiata Fornix Internal capsule Gray matter Third ventricle White matter Pons Projection fibers Medulla oblongata (a) Copyright © 2010 Pearson Education, Inc. Decussation of pyramids (b)

C. Basal Nuclei These represent the third region of the cerebral hemisphere. The basal nuclei consist of the: – caudate nucleus, – putamen and – the globus pallidus. Copyright © 2010 Pearson Education, Inc.

The basal nuclei receive input from the entire cerebral cortex. They appear to be important in starting and stopping the intensity of movements initiated by the cerebral cortex. They are important in our ability to multitask. Copyright © 2010 Pearson Education, Inc.

Together the putamen and globus pallidus form the lentiform nucleus that flanks the internal

Figure 12. 11 b Basal nuclei (1 of 2). Anterior (b) Copyright © 2010 Pearson Education, Inc. Posterior Cerebral cortex Cerebral white matter Corpus callosum Anterior horn of lateral ventricle Caudate nucleus Putamen Lentiform Globus nucleus pallidus Thalamus Tail of caudate nucleus Third ventricle Inferior horn of lateral ventricle

Figure 12. 11 b Basal nuclei (2 of 2). Cerebral cortex Cerebral white matter Corpus callosum Anterior horn of lateral ventricle Caudate nucleus Lentiform nucleus Thalamus Third ventricle Inferior horn of lateral ventricle (b) Copyright © 2010 Pearson Education, Inc.

Disorders of the Basal Nucleus The basal ganglia play a central role in a number of neurological conditions. The most notable are, Parkinson’s disease and Huntington's disease. Basal ganglia dysfunction is also implicated in some other disorders of behavior control such as Tourette’s syndrome, and obsessive compulsive disorder (OCD), Copyright © 2010 Pearson Education, Inc.