Class Notes (839,092)
Canada (511,185)
Psychology (6,277)
Lecture 7

Psych 2220A Lecture 7

8 Pages

Course Code
Psychology 2220A/B
Scott Mac Dougall- Shackleton

This preview shows pages 1,2 and half of page 3. Sign up to view the full 8 pages of the document.
Psych 2220A Lecture 7 Hearing • The auditory system (7.2) • Auditory perception and stream segregation (not in text in detail) Auditory Cortex • Auditory cortex is located in the temporal lobe • Core region: includes primary cortex • Belt surrounds the core region –Aband of secondary cortex • Secondary cortex outside the belt – Referred to as parabelt areas • About ten separate areas of secondary auditory cortex in primates Organization of PrimateAuditory Cortex • Functional columns (cells of a column respond to the same frequency) • Tonotopic organization • Secondary areas do not respond well to pure tones, likely important for more complex features of sounds Stimuli • Still much to learn about dimensions of sounds processed in different parts of auditory cortex • Challenge of using simple sound stimuli (tones) – easy to manipulate, but lack complex features that the cortex may be designed to process – many cortical cells respond to vocalization sounds Two Streams ofAuditory Cortex • Auditory signals are conducted to two areas of association cortex – Prefrontal cortex – Posterior parietal cortex • Anterior auditory pathway may be more involved in identifying sounds (what) • Posterior auditory pathway may be more involved in locating sounds (where) Auditory-Visual Interactions • There is evidence for interactions between the auditory and visual systems – e.g. some posterior parietal neurons with both visual and auditory receptive fields • Interaction in primary sensory cortices indicate that sensory system interaction is an early and integral part of sensory processing McGurk effect • Phonemes often vary continuously, but are perceived categorically • Visual and auditory input of two phonemes can give rise to perception of intermediate phoneme! • Psych 2220A Lecture 7 Where Does the Perception of Pitch Occur? • Most auditory neurons respond to changes in frequency rather than pitch • One small area just anterior to primary auditory cortex has neurons that respond to pitch rather than frequency – May be where frequencies of sound are converted to perception of pitch Effects of Damage to theAuditory System • Lesions of auditory cortex in rats results in few permanent hearing deficits • Lesions in monkeys and humans hinder sound localization and pitch discrimination • Deafness in humans – Total deafness is rare, due to multiple pathways – Two kinds: conductive deafness (damage to ossicles) and nerve deafness (damage to cochlea) – Partial cochlear damage results in loss of hearing at particular frequencies Auditory SceneAnalysis • Cocktail party phenomenon – Pop-out of salient stimuli • Stream segregation – Complex auditory stream partitioned into individual auditory objects • Completion of partial stimuli – Specialized perception of phonemes and speech Stream segregation •Auditory streams segregate based on pitch similarities and timing Completion of Partial Stimuli • Picket fence effect * Somatosensory System Text Section 7.3 * Somatosensory Homunculus • Homunculus = “little man” • Shows the relative size of the somatosensory representation devoted to various body parts • Do you notice a relationship between the size of the representation and the sensitivity (e.g., two-point touch threshold)? Somatosensory System: Touch and Pain • Somatosensory system is three separate and interacting systems: • Exteroceptive – external stimuli • Proprioceptive – body position • Interoceptive – body conditions (e.g., temperature and blood pressure) Psych 2220A Lecture 7 Cutaneous Receptors • Free nerve endings – Temperature and pain • Pacinian corpuscles –Adapt rapidly, large and deep; onion-like – Respond to sudden displacements of the skin • Merkel’s disks – gradual skin indentation • Ruffini endings – gradual skin stretch Dermatome • The area of the body innervated by the left and right dorsal roots of a given segment of spinal cord • Considerable overlap between adjacent dermatomes Two Major Somatosensory Pathways • Dorsal-column medial-lemniscus system – Mainly touch and proprioception – First synapse in the dorsal column nuclei of the medulla •Anterolateral system – Mainly pain and temperature – Synapse upon entering the spinal cord – Three tracts – spinothalamic, spinoreticular, spinotectal • Lots of overlap in function of these two pathways Spinal Injury • Transection of both paths leads to complete lack of sensation below the level of the cut CorticalAreas of Somatosensation • Primary somatosensory cortex (SI) – Postcentral gyrus – Somatotopic organization (somatosensory homunculus) – more sensitive, more cortex – Input largely contralateral • SII – mainly input from SI – Somatotopic; input from both sides of the • Much of the output from SI and SII goes to association cortex in posterior parietal lobe Platypunculus? • Platypus homunculus (platypunculus?) – Platypus has tactile and electrosensory receptors – bill = 75% of S1 Receptive Fields of S1 Neurons • Similar to V1, many neuron’s receptive fields have antagonistic excitatory and inhibitory areas • Columnar organization: in a column receptive fields are for same part of the body Psych 2220A Lecture 7 Effects of Damage to the Primary Somatosensory Cortex • Effects of damage to the primary somatosensory cortex are often mild – Likely due to numerous parallel pathways Somatosensory System andAssociation Cortex • Highest level of sensory hierarchy are areas of association cortex in prefrontal and posterior parietal cortex • Posterior parietal cortex contains bimodal neurons – Neurons that respond to activation of two different sensory systems –Allow integration of visual and somatosensory input SomatosensoryAgnosias • Astereognosia – inability to recognize objects by touch – Pure cases are rare – other sensory deficits are usually present • Asomatognosia – the failure to recognize parts of one’s own body Perception of Pain • Despite its unpleasantness, pain is adaptive and needed • No obvious cortical representation of pain (although the anterior cingulate gyrus appears involved in the emotional component of pain) • Descending pain control – pain can be suppressed by cognitive and emotional factors Descending Pain Control • Circuitry identified by the following studies: • Electrical stimulation of the periaqueductal gray (PAG) has analgesic effects • PAG and other brain areas have opiate receptors • Existence of endogenous opiates (natural analgesics) – endorphins Neuropathic Pain • Severe chronic pain in the absence of a recognizable pain stimulus • Likely from pathology of nervous system linked to an injury • Some evidence for aberrant glial cell signals triggering neural pain pathways Chemical Senses: Smell and Taste • Olfaction (smell) – Detects airborne chemicals • Gustation (taste)
More Less
Unlock Document

Only pages 1,2 and half of page 3 are available for preview. Some parts have been intentionally blurred.

Unlock Document
You're Reading a Preview

Unlock to view full version

Unlock Document

Log In


Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.