Chapter 12 Memory

Memory refers to the storage and retrieval of information. No absolute boundaries between learning and memory. Learning and memory may be viewed as a being on a time continuum.

Divisions of Long-term Memory

Locating the Engram Karl Lashley observed the effects of lesions on rats’ maze learning. The larger the amount of cortex damaged, the more errors the rats made. Lashley believed that the engram was distributed across the cortex.

Patient H.M. and Memory Large areas of H.M.’s temporal lobes were surgically removed. H.M.’s personality and IQ were not affected. H.M. experienced profound anterograde amnesia. Courtesy Dr. Suzanne Corkin, Massachusetts Institute of Technology

H.M.’s Memories Are Not Equally Affected Short-term memory allowed H.M. to converse. H.M. retained the ability to learn procedural tasks. H.M.’s deficits appear in explicit memory tasks.

The Delayed Nonmatching to Sample Task Monkeys with medial temporal lobe damage do poorly on the DNMS task. The DNMS task requires the ability to form long-term memories.

The Anatomy of the Hippocampus in Humans

Producing Long-Term Potentiation in the Rat

Long-Term Potentiation

LTP and the NMDA Receptor

LTP Shares Characteristics with Long-term Memory Both LTP and long-term memories last indefinitely. Both LTP and long-term memories result from very brief input. LTP is consistent with cellular learning models proposed by Donald Hebb.

The Hippocampus and Human Memory The right hippocampus is active during spatial memory processing and the left hippocampus is active during verbal memory processing. Rostral portions of the hippocampus are more active during encoding, and caudal portions are active during retrieval. The hippocampus does not store memories, but transfers them from short to long-term storage.

Patient N.A. A fencing foil produced a lesion to N.A. ’ s left dorsomedial thalamus. N.A. experienced profound anterograde amnesia and some retrograde amnesia. N.A. ’ s memory loss was similar to H. M. ’ s. Courtesy L.R. Squire, University of California San Diego

The Basal Ganglia and Procedural Memory Lesions of the hippocampus impaired declarative memories (remember where you went last time). Lesions of the caudate nucleus impaired procedural memories (food is in the arms that have small lights). Patients with Huntington’s disease and Parkinson’s disease have procedural memory deficits, but not declarative memory deficits.

Unusual Memory Phenomena Repression Flashbacks Flashbulb memories Stress affects the amygdala and hippocampus Cortisol may damage the hippocampus KHBS KHOG/AP/Wide World

Alzheimer’s Disease Alzheimer’s disease begins with mild memory loss, and progresses to loss of language, social skills and problem solving. Hallucination and delusion may occur in later stages of the disease. Eventually, the disease is fatal.

Factors Underlying Alzheimer’s Disease Neurofibrillary tangles result from the breakdown of the tau protein, which supports the microtubules of the cytoskeleton. Abnormal amyloid forms senile plaques. Deterioration along pathways originating in the basal forebrain and limbic system.

Progression of Alzheimer’s Disease