1 / 28

Last Lecture

Last Lecture. The Wernicke-Geschwind Model of Reading Category-specific semantic deficts and the representation of meaning Introduction to the Frontal Lobes. This Lecture. Frontal Lobe Anatomy Inhibition and voluntary control A model task: working memory . Announcements. FINAL EXAM:

carolena
Download Presentation

Last Lecture

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Last Lecture • The Wernicke-Geschwind Model of Reading • Category-specific semantic deficts and the representation of meaning • Introduction to the Frontal Lobes

  2. This Lecture • Frontal Lobe Anatomy • Inhibition and voluntary control • A model task: working memory

  3. Announcements FINAL EXAM: • 182 Dennison • Wednesday, 4/19 • 4:00 pm - 6:00 pm. • Please contact us immediately if this poses a conflict.

  4. Prefrontal cortex • ~ 1/3 of cortical surface • Most recently evolved • Well developed only in primates • the advent of the human species: "age of the frontal lobe" • develops late in ontogeny • differentiation through age 1 • maturation through age 6

  5. Connectivity of Prefrontal regions • input from association cortex(occipital, parietal, temporal & olfactory areas) • convergence of higher-orderinputfrom all modalities. • reciprocal connections:prefrontal processing modulates perceptual processing. • LIMBIC connections(memory/emotion) • Input to premotor areas- controls/programs behavior.

  6. Premotor & Motor Areas • Premotor areas (6) - input from prefrontal regions and parietal association areas (5,7). • Area 4: primary motor cortex • input from premotor area (6) and area 44 • sends output to spinal cord, and other motor structures (basal ganglia) • Frontal network controls voluntary, planned actions.

  7. Frontal Release signs Re-emergence of "primitive" reflexes following frontal damage. • grasp reflex: forceful grasping of an object that contacts palm or sole of foot. • sucking reflex: elicited by touching the lip • groping reflex: involuntary following with hand /eyes of moving object • stimulus capture: utilization behavior The frontal lobes normally inhibit stimulus-bound reflexes.

  8. Mediate voluntary control of behavior... ANTI-saccade task • saccade AWAY from an eccentric target • patients w/ prefrontal damage including FEF (Area 8): • reflexive saccades to the target. • Cannot correct error and make anti-saccades • e.g., left lesion patients impaired on right anti-saccades +

  9. Poor performance on Anti-saccade task • Why more reflexive saccades? • Superior colliculus- control rapids, stimulus-driven eye movements. • Disinhibited by frontal lobe damage, "releasing" reflexive glances • Why were Anti saccades impaired? • Difficulty forming representation of goal to control voluntary behavior.

  10. Model task to study frontal lobe function: Delayed Response Task • Correct response requires keeping baited well in mind. • Monkeys and humans w/lesions of LPFC fail these tasks. • Infants younger than 12 months also fail versions of these tasks.

  11. Delayed Saccade Task (Goldman-Rakic) • Single unit recordings from principal sulcus (Brodmann's 46). TASK: • Cue one of 8 locations • 3 sec. delay • fixation removed signaling GO • Saccades to remembered location

  12. Cognitive Role of area 46 • Delay activity -- location specific • Delay activity reduced when monkeys made errors. • Lesions of 46 impair performance on this task. Interpretation: • Neural activity corresponds to mental representation of a GOAL • The goal is maintained "on-line" available for use. • This is working memory.

  13. Without goal representation... Behavior is determined by • reflex • habit • past-reward (perseveration) • immediate stimulus conditions Rather than by intentions that integrate the relevant current spatial and temporal context.

  14. Frontal Lobes and Working memory... A system for maintaining and manipulating information to perform complex cognitive activities (Baddeley, 1992).

  15. EXECUTIVE visuo- spatial sketch pad phono- logical loop Working Memory • on-line store • short-term retention (approx. 10 sec) • executive processes • rehearsal processes • material specific buffers • verbal (phonological loop) left hem. • spatial (visuo-spatial sketchpad) right hem.

  16. Executive Functions of Prefrontal Cortex Aleksandr Luria (1966) Programming, regulating, monitoring Smith & Jonides (1999) Attention/inhibition, task management, contextual coding, planning, monitoring

  17. Verbal WM Tasks • M R • • K D Verbal 500 msec m Memory 500 msec 3000 msec 1500 msec • M M • Verbal M M • 3200 msec Control m 500 msec 300 msec 1500 msec

  18. Spatial WM Tasks + + + Spatial 500 msec + Memory 500 msec 3000 msec 1500 msec + + Spatial + 3300 msec + Control 500 msec 200 msec 1500 msec

  19. Regions of Significant Activation Verbal Spatial

  20. Hypothesized Working Memory Circuitry • Frontal sites control rehearsal and manipulation of stored information. • Parietal sites control the storage of this information. Anterior Posterior

  21. Aging and Working Memory Synapses in LPFC • WM - contributes broadly to higher cognition. • WM declines w/age. • PFC atrophies w/ age. • How does the neural substrate of WM change w/age? Birth 1 yr 60 100 (after Huttenlocher, 1979)

  22. VERBAL-Recognition Errors 10 8 6 Errors( %) 4 2 0 Young Seniors Performance Results • Seniors made more Verbal errors than Young(p = 0.02) • Senior and Young groups had equal Spatial accuracies (p = 0.6) SPATIAL-Recognition Errors 10 9 8 7 6 5 Errors (%) 4 3 2 1 0 Young Seniors

  23. Regions of Activation(Reuter-Lorenz et al., 2000)

  24. *** 2.0 2.0 LH RH LH RH *** 1.8 1.8 *** 1.6 1.6 *** 1.4 1.4 *** 1.2 1.2 1.0 1.0 Percent Activation Change 0.8 0.8 0.6 0.6 0.4 0.4 0.2 0.2 0.0 0.0 Younger Older Younger Older -0.2 -0.2 Neuroimaging Results (verbal) Anterior Regions Posterior Regions (* = p < .05 ** = p ≤ .02 *** = p < .005)

  25. LH RH LH RH Neuroimaging Results Spatial Anterior ROIs Posterior ROIs 2.0 2.0 1.8 1.8 1.6 1.6 1.4 1.4 1.2 1.2 *** 1.0 1.0 ** Percent Activation Change ** ** ** 0.8 0.8 ** ** 0.6 0.6 0.4 0.4 0.2 0.2 0.0 0.0 Younger Older Younger Older -0.2 -0.2 (* = p < .05 ** = p ≤ .02 *** = p < .005)

  26. Aging and Working Memory: Summary • Neural substrate for WM is affected by aging. • Selectivity: Frontal circuitry more vulnerable. • Decreased lateralization. • Compensatory? • Recruitment as a “neural strategy” to cope with age-related loss of neural efficiency.

  27. Long Term Memory and its Dysfunction • Memory: the ability to retain & recollect the contents of our experience • typically multimodal • rich in associations • Expanding the definition to include... the ability to acquire new skills & demonstrate improved performance as a result of experience.

  28. Human Amnesia • Anterograde: Inability to acquire NEW memories. • Retrograde: Inability to recollect OLD memories.

More Related