The cerebral cortex has four lobes, each is specialized for different activities. The lobes and some of their functions: –Occipital lobe- initial processing of visual input –Temporal lobe - primary auditory cortex, integration of multiple sensory inputs, Wernicke’s area –Parietal lobe - somatosensory processing. Each region of parietal cortex receives somesthetic and proprioceptive input from a specific body area, mostly from the opposite side of the body. –Frontal lobe - voluntary motor activity, speaking ability (Broca’s area), and elaboration of thought. Stimulation of different areas of its primary motor cortex moves different body regions.

Frontal lobe Central sulcus Parietal lobe Parietooccipital notch Occipital lobe Cerebellum Brain stem Temporal lobe Lateral fissure

Occipital lobe Primary visual cortex

Wernicke’s area Temporal lobe Primary auditory cortex

Central sulcus Somatosensory cortex Posterior parietal cortex Wernicke’s area Parietal lobe

Left hemisphere Cross-sectional view Temporal lobe Sensory homunculus

Primary motor cortex Central sulcus Broca’s area Frontal lobe Premotor cortex

Left hemisphere Cross-sectional view Temporal lobe Motor homunculus

Central sulcus Parietal-temporal-occipital association cortex Limbic association cortex Prefrontal association cortex Association areas of the cortex carry out many higher functions: Association Areas of the Cerebral Cortex planning for voluntary activity, decision-making, creativity, and developing personality traits integrates somatic, auditory, and visual sensations from these three lobes involved with motivation, emotion, and memory

Sensory input Primary sensory areas (somatosensory, 1 o visual, 1 o auditory cortices) Higher sensory areas Association areas Higher motor areas Primary motor areas Motor output

Fundamentals of Sensory Systems A. General Concepts in Sensation and Perception Function of sensory systems Visceral versus sensory afferents Sensation versus perception Psychophysics B Receptor Structure and Function Specific for particular forms of energy Vary across sensory systems Perform common function (transduction) in unique ways Sites of convergence and divergence C. Peripheral Organization Labeled Line Principle Topographic projections Mechanisms to enhance contrast sensitivity D.Central Processing Includes sensory cortex and association areas Response Maps and Plasticity

Variable perceptions from the same visual input Do you see two faces in profile, or a wine glass?

Do you “see” a white square that is not really there?

Receptor Morphologies Reflect Specialized Functions Photoreceptors Mechanoreceptors Thermoreceptors Osmoreceptors Chemoreceptors Nociceptors CATEGORIES OF RECEPTORS

Receptor Potentials are GRADED Generator potential: Somatosensory Receptor potential: Auditory/Visual

Stimulus off Slowly adapting Stimulus on Time Receptor potential (mV) Stimulus strength Tonic Receptors Muscle Stretch, Proprioception

Stimulus off Rapidly adapting Stimulus on Time Receptor potential (mV) Stimulus strength Off response Phasic Receptors skin touch

Doctrine of Specific Energy or Labeled Line Principle “Phantom” Pain

Coding of Sensory Information Stimulus PropertyCoding Mechanism Stimulus ModalityDistinguished by the type of receptor activated (what)and the specific pathway that transmits this information to a particular area of (sensory) cerebral cortex Stimulus LocationDistinguished by location of activated receptive (where)field, and the pathway that is activated to transmit this information to the area of cerebral cortex representing that location. Stimulus IntensityDistinguished by the frequency of action (how much?)potentials and the number of receptors activated.

Receptor endings of afferent neurons Receptive fields on skin surface Receptive Field Size Determines Acuity Sensory homunculus

Stimulated less Stimulated most Receptor pathways Skin surface Frequency of action potentials Baseline level of activity Location on skin Mechanisms To Enhance Acuity

Transmission stopped Lateral inhibition Frequency of action potentials Baseline level of activity Area of sensation on skin Transmission stopped Transmission continues

Center/Surround Organization of Receptive Fields

Sensory Pathways: CNS

Primary Sensory and Association Areas of Cerebral Cortex

Practical Applications