Implict vs Explicit memory

Implicit memory

• Unconscious

• Word list tasks: stem completion, fragment completion, degraded naming

• No difference after deeper processing

• Changing modality (eg learn words through reading but present through speech) reduces performance

• Not impaired by medial temporal lobe damage induced amnesia

• Patient MS had right-side occipital lesions and could not remember implicitly but could explicitly, very unusual

• Gabrieli et al. (1995) Patient MS struggled with visual priming tasks but was fine at recall and recognition. Most of right occipital lobe was removed at age 14 to manage epilepsy. He has high IQ, manages a software company and generally copes well with cognitive tasks. Other patients and controls could identify a word quicker after priming (briefly seeing it) but he didn’t. Most patients do better with visual priming than auditory priming (for a written task) but MS didn’t. Priming by studying words in advance (explicitly) did improve his performance which was normal.

• fMRI shows activation in fusiform cortex (posterior of brain) during certain implicit processing

Explicit memory

• Conscious

• Word list tasks: recall, recognition

• Improved by deeper processing

• Changing modality (eg learn words through reading but present through speech) improves performance

• Damaged significantly in amnesiacs. Supported by evidence from patients with medial temporal lobe amnesia (implicit intact)

• FmRI shows activation in medial temporal lobe during storage/retrieval

• Graf et al. (1984) amnesics do worse than controls on free & cued recall and recognition memory (testing explicit memory) and slightly better on word completion (testing implicit memory)

Differences

• Use different brain regions so are functionaly separate systems, supported by fMRI evidence