Last Lecture Frontal Lobe Anatomy Inhibition and voluntary

Last Lecture Frontal Lobe Anatomy Inhibition and voluntary control A model task: working memory +

This Lecture Long Term Memory role of hippocampus in consolidation role of frontal regions in encoding and retrieval right frontal regions and representation of self. . .

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

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

Human Amnesia Scoville & Milner (1957) H. M. bilateral removal of hippocampus (medial temporal lobes). Wada testing to avoid bilateral hippocampectomies. Unilateral removals: material -specific deficit: (Rightnonverbal; Left: verbal)

Case H. M. -- PROFOUND ANTEROGRADE AMNESIA High Average intelligence STM: normal- digit span 7 forward; 5 backward Can converse normally, perform mental math No post-operative personality changes Unable to acquire new memories. . . all modalities all material (verbal, nonverbal) names, people, places, events, route finding all are affected.

Early animal models of HM were unsuccessful WHY? (Hint: remember what happened with blindsight) Testing the wrong type of memory What Amnesics can learn: Milner (1962) mirror drawing Warrington & Weiskrantz (1968) perceptual learning (degraded cues, priming) Weiskrantz & Warrington (1979) classical conditioning

Types of Long Term Memory

Declarative/Explicit consciously accessible Episodic: personal/public episodes Semantic: facts, events, routes Tested with recall / recognition: "Have you seen this before? "; "Can you remember. . . ? "; "Is this one of the items you studied. . . ? ”

Nondeclarative/Procedural/Implicit Does not require conscious recollection Examples: conditioning skills (motor skills, mirror reading) priming (e. g. stem completion)

Skill Acquisition Mirror drawing improves Amnesics = Controls

An example of the dichotomy. . . Phase 1 Phase 2 Read & rate words (living/non): Lead Bear Fear Work. . . EXPLICIT TEST: "Complete stem with a word you just read" lea_ bea_ OR IMPLICIT TEST: "Complete stem with first word that comes to mind" lea_ ---> lead or leaf bea_ ---> beat or bear

Priming is spared in Amnesia Amnesics cannot recall study items. But stored representation is accessed automatically.

The Hippocampal circuit & Explicit Memory Hippocampus - part of a circuit with input to & from parietal, temporal, frontal lobes & limbic system (amygdala).

Hippocampus

The Hippocampal circuit & Explicit Memory Hippocampus - part of a circuit with input to & from parietal, temporal, frontal lobes & limbic system (amygdala). CA 1 , CA 2 , CA 3 layers of HPC form a circuit allowing access to cortex CA 1 layer - sensitive to anoxia & epileptic activity (CASE R. B. ) Damage to HPC or its inputs/outputs --> LTM impairment

Role of Hippocampus in Explicit Memory NOT the location of LTM NOT necessary for retrieval of LTM NOT the location of STM HPC: immediate experience --> LT memories CONSOLIDATION Explicit memory - stores single events w/ context. Learning is fast (one-trial learning-- but forgetting endures). Representations are accessible by various cognitive systems modality-general give rise to sense of familiarity.

Implicit memory. . . Reactivation of the processing structures engaged during learning. Learning is incremental, gradual, slow Representations are specific to a task and or the learning modality. Involves multiple systems (cortex, basal ganglia) More on the encoding and retrieval of explicit LTM. . .

Frontal Contributions to LTM Recency Judgments knowledge of temporal context give a list of items probe w/ two items asking: “Which one of these items came most recently? ”

Frontal Contributions Source Memory ability to identify (remember) the context in which a memory was acquired task: judge which of two characters uttered a particular fact. Mt. Everest Keeps growing Marco Polo was Venetian

HERA: Hemispheric Encoding/Retrieval Asymmetry (Tulving et al. , 1994) PET studies w/normal subjects show Left Hem. is critical to encoding into LTM Lateral Prefrontal areas all materials: verbal & nonverbal Why? associating meaning with events Right Hem. is critical to retrieval from LTM Lateral Prefrontal areas all materials: verbal & nonverbal Why? memory requires reflection about self / personal experience

Right Frontal Lobe & Self Craik et al. , 1999 - PET study with 4 conditions How well does the word stubborn describe. . . You? Lee Bollinger? How socially desireable? How many syllables? RESULT: Only self-referential instruction activated Right prefrontal cortex ( same areas activated by memory retrieval) Conclusion: Right frontal regions are important for representation of self.

Memory Summary WM vs. LTM Explicit (personal episodes, semantics/facts) Amnesia -- anterograde or retrograde Establishing new explicit memories requires LTM: IMPLICIT vs. EXPLICIT encoding, consolidation, retreival hippocampus -- consolidation (HM & RB) HERA: Left frontal- encoding (context info) Right frontal- retrieval (self)