Model of Memory RETRIEVAL Atkinson & Shifrin ATTENTION Sensory Signals Sensory Memory Short-Term Memory Long-Term Memory REHEARSAL

Long-term Memory How long is it? - persists indefinitely (from seconds to decades) - persists without active rehearsal What types of LTM are there?

Long-term Memory Where does the distinction between LTM types come from?

Long-term Memory Where does the distinction between LTM types come from? Brenda Milner Turns 89 this year. Last publication was in 2005!

Patient H.M. “Loss of Recent Memory After Bilateral Hippocampal Lesions”, Scoville and Milner (1957) onset of epilepsy at age ten, perhaps due to bike accident (wear a helmet!) 1953 - underwent temporal lobectomy to reduce seizure activity Wear a helmet! First study to localize memory to a specific structure The surgery was experimental!

The imaging technology that was available at the time…

Patient H.M. severe anterograde amnesia temporally graded retrograde amnesia

Patient H.M.

Patient H.M. Memory and perceptual skills are dissociable. Lesions of the MTL produce amnesia for recent but not remote events. There are multiple long-term memory systems in the brain.

Patient H.M. What’s new with Patient H.M.? Suzanne Corkin et al. (1997) used MRI to assess lesion extent First “experimental” brain surgery, then “experimental” MRI (clips used in surgery may be magnetic)

Patient H.M. perhaps H.M.’s lesion is not as big originally thought, at least in terms of hippocampal damage most of amygdala, entorhinal cortex (major input to HPC), and large portion of HPC gone or atrophied mammillary nuclei shrunken cerebellar atrophy Textbook suggests that Scoville was way off. Don’t forget Korsakoff’s syndrome. Pretty good, considering the tools available.

Patient H.M. So what can H.M. do?

Patient H.M. So what can H.M. do?

Picture of house before and after surgery, H. M Picture of house before and after surgery, H.M. recalls the layout of the newer house. Acquired this info after his surgery.

Patient H.M. fMRI of H.M. during novel picture encoding Some of the surrounding tissue is functional… caudal parahippocampal gyrus activation (same as controls)

Patient K.C. developed amnesia after motorcycle accident (really, wear a helmet!) damage to MTL, frontal, parietal and occipital cortices suffered from source amnesia - remember the info, just not where/when you learned it

Priming tasks, can retain info for up to 12 months, similar to controls (as can H.M.)

Other examples of priming tasks that MTL patients can do… No memory of episode during which task was learned. You can train someone on sequence task, they will get better although not necessarily aware of the pattern (can’t tell you the pattern explicitly)

Long-term Memory so we have a single dissociation what about people that have an intact declarative memory system yet present with difficulties in non-declarative tasks?

Patient M.S. opposite pattern of results from H.M./K.C. intact declarative memory problems with priming tasks Problem with implicit perceptual priming task

Patient M.S. Extrastriate cortex. Visual association area, shape recognition, attention?

Long-term Memory there are multiple memory systems in the brain. explicit (declarative) and implicit (non-declarative) memory can be doubly dissociated can anyone see a problem with using human subjects? Lack of control of size/location of the lesion.