Sensory Memory and Working Memory

1. Sensory Memory and Working Memory

2. Sensory Memory • Brief • Iconic/echoic • High capacity • Pre-attentive • Is there a Neural Correlate of Sensory Memory?

3. Is there a Neural Correlate of Sensory Memory? • Stimuli that deviate from a regular sequence cause a change in the ERP/MEG called the mismatch negativity/mismatch field • MMN/MMF only occurs when stimuli are close together in time • Thought to reflect an automatic response to detection of difference between current and previous stimuli

4. Short-Term Memory • Duration of seconds • Limited capacity • Not pre-attentive

5. Neuropsychology of STM • Patient E.E. • Reduced digit-span • Normal speech, comprehension • Normal long-term memory • Why is this finding puzzling? Removal of tumor in L. Angular Gyrus

6. Working Memory • STM has been replaced by Working Memory model

7. Working Memory • STM has been replaced by Working Memory model • “Transient representations of task relevant information” • Limited capacity store AND mechanism for working with that information • Are there brain structures associated with these functions?

8. Working Memory • Left Supramarginal Gyrus and left premotor lesions associated with difficulty holding strings of words in mind • Right parieto-occipital damage associated with visuospatial memory deficits • Thus these are doubly dissociated

9. Working Memory and Frontal Cortex • An important aspect of working memory is maintaining a representation of previous information while it remains relevant to a current goal • This information may come via sensory systems, or it may be reactivated from a long-term store

10. Working Memory and Frontal Cortex • Animal lesion studies reveal that the Lateral Prefrontal cortex is critical for maintaining these “working” representations

11. Working Memory and Frontal Cortex • Goldman-Rakic et al. • Spatial working memory is dissociable from long-term associative memory

12. Working Memory and Frontal Cortex • Working Memory Task • Well is baited with food • Target well changes from trial to trial • Monkey’s view is blocked for a delay interval • Monkey must indicate the baited well to get rewarded • Requires maintained representation of current target location

13. Working Memory and Frontal Cortex • Associative Memory Task • Each well is indicated by a picture • Target is always associated with the same picture(s) • Monkey’s view is blocked for a delay interval • Monkey must indicate the baited well to get reward • Requires recall of cue from LTM

14. Working Memory and Frontal Cortex • Goldman-Rakic et al. • Spatial working memory is dissociated from long-term memory • Lesions cause deficit in working memory task but not association task

15. Working Memory and Frontal Cortex • Goldman-Rakic et al. • Spatial working memory is dissociable from recognition memory

16. Working Memory and Frontal Cortex • Working Memory Task • 1 of 3 objects is indicated to the monkey • View is blocked for a delay • 2 of the 3 objects are presented • Monkey must select the non-match object • Requires working memory because no other cues differentiate the two objects • Recognition Memory Task • Same as Working memory task except… • After delay, indicated object is paired with a novel object • Monkey must select novel object • Requires recognition memory to differentiate unfamiliar from familiar objects

17. Working Memory and Human Frontal Cortex?

18. Working Memory and Human Frontal Cortex BOLD signal in lateral prefrontal cortex (area 46) is greater for memory task than for color Discrimination task