Priming, Implicit Memory, and the Brain: A Neuroimaging Perspective Daniel L. Schacter

Priming, Implicit Memory, and the Brain:

A Neuroimaging Perspective

Daniel L. Schacter Harvard University

Acknowledgements

Memory Lab, Harvard Psychology

Donna Addis

Elissa Aminoff

Elizabeth Chua

Rachel Garoff-Eaton

Angela Gutchess

Dale Stevens

Gagan Wig

Alana Wong

Athinoula A. Martinos Center for Biomedical Imaging

Supported by NIMH and NIA

MYSTERY

APRICOT

CUPCAKE

ASSASSIN

_ _ES_ _X

_UP_ _KE

Tulving, Schacter, & Stark (1982)

Picture Fragment ID after 17 Years

(M Age = 39.2; Mitchell, 2006)

30

35

40

45

50

55

60

65

70

Old New

Some Properties of Priming on Stem Completion, Fragment Completion and Identification Tests

*Unaffected or even reduced by semantic or elaborative encoding manipulations that enhance recall and recognition.

*Sensitive to changes between study and test in the physical features of target items: sensory modality, word font, case. Such changes typically have smaller effects on recall and recognition.

*Typically preserved in amnesic patients with impairments on recall and reocgnition tests.

Characterizing Dissociations: Memory Systems

Priming on tests such as completion and identificationis little affected by semantic processing and highlydependent on physical features of stimuli.

Led to postulation of perceptual representation system(‘PRS’): involves storage/retrieval of modality-specific information that supports identification of words/objects (Schacter, 1990;Tulving & Schacter, 1990).

“Pre-semantic” collection of susbsystems (visualword form, auditory word form, structural description) that depend on posterior cortical brain regions, nothippocampus/MTL; should be preserved in amnesia.

Object Priming Paradigm

+

+

+

+

+

+

+

+

+

+

+

+

STUDY TEST

2 SECBETWEENSTIMULI

Behavioral Performance at Test

NOVEL REPEATED 0

450

500

550

600

650

700

750

800

850

900

RE

AC

TIO

N T

IME

(M

SE

C)

+ +

Novel > Repeated Same

• Left anterior inferior frontal cortex (BA 47, 45)

• Bilateral fusiform, extending into parahippocampal cortex (BA 37, 19)

Reduced activation (indicating priming) for repeated objects in multiple regions, including:

Priming-related activation decreases

Specificity of Priming-Related Specificity of Priming-Related ReductionsReductions

Neural correlates of priming for:

• Novel objects

• Repeated same objects

• Repeated different objects

18 subjects scanned while undertaking size judgements of visually-presented objects.

Koutstaal et al. (2001) Neuropsychologia

Fusiform Laterality EffectFusiform Laterality Effect

Repeated Different > Repeated SameRepeated Different > Repeated Same

• Bilateral fusiform (BA 37, 19).

• Greater effect of exemplar change in Right than Left fusiform cortex

Greater activation (indicating less priming for Different) in:

Explaining Activation Decrease in Object Priming

Wiggs, C. L., & Martin, A. (1998). Properties and mechanisms of perceptual priming. Current Opinion in Neurobiology.

“Neural Tuning”

High PrimeNovel

“Bigger than a shoebox? (yes/no)”

1.Start Phase

2.Switch Phase

“Smaller than a shoebox? (yes/no)”

High PrimeNovel

Novel Low Primed High Primed

3.Return Phase

“Bigger than a shoebox? (yes/no)”

Low Primed Novel High Primed

Low PrimeNovel Novel Low Prime

n = 16, Event Related, 4 - Cycles

Is Object Priming Response Specific?

Dobbins, Schnyer, Verfaellie & Schacter (2004) Nature

600

700

800

900

1000

1100

Cue Reversal - fMRINovel Low High

Start Switch Return

Mea

n R

eact

ion

Tim

e -

mill

isec

onds

a

Is Object Priming Response Specific?

Dobbins, Schnyer, Verfaellie & Schacter (2004) Nature

-15

Start Switch Return

Mean “Neural Priming”

-0.04

0.00

0.04

0.08

0.12

-0.02

0.00

0.02

0.04

0.06

0.08

0.10

0.12

PFC

Fusiform

Is Object Priming Response Specific?

.00

.10

.20

.30

.00

.10

.20

.30

PFC

Fusiform

Start Switch Return

ForgettingControl

Dobbins, Schnyer, Verfaellie & Schacter (2004) Nature

Is Object Priming Response Specific?

Relation to Behavior

-15

Both fusiform and PFC “neural priming” scores predictedbehavioral priming scores, each accounting for unique variance.

PFC (not fusiform) neural priming predicted size of behavioralslowing that occurred when cue was switched…suggeststhat lack of activity is a marker of automaticity.

Frontal Temporal Perceptual

-Dobbins et al. (2004)

-Maccotta & Buckner (2004)

-Lustig & Buckner (2004)

-Bergerbest et al. (2005)

-Golby et al. (2005)

-Oranfidou et al. (2006)

-Bunzeck et al. (2006)

-Turk-Browne et al. (2006)

-Carlesimo et al. (2003)

Is there a correlation between behavioral & neural priming?

-Dobbins et al. (2004)

-Turk-Browne et al. (2006)

A

Stimulus Specificity

MostLeast

LR

Schacter, Wig & Stevens (2007). Curr Opin Neurobiol

A multiple component model of priming

A

D

A

Stimulus Specificity

MostLeast

LR

Schacter, Wig & Stevens (2007). Curr Opin Neurobiol

A multiple component model of priming

-Amodal

-Priming across abstract representations

-Sensitive to changes in stimulus-decision mapping

A

D

A

Stimulus Specificity

MostLeast

LR

Schacter, Wig & Stevens (2007). Curr Opin Neurobiol

A multiple component model of priming

-Amodal

-Priming across abstract representations

-Sensitive to changes in stimulus-decision mapping

-Most consistently correlated with behavior

Study PhaseFor each of 3 runs at study, 144 shapes were presented (16 sets of 9 exemplars)

Each set alternated in spatial position to the right or left of fixation

Pres. Time = 2.5 sec

Instructions: remember each shape and side of the screen

NonstudiedPrototype Exemplar Exemplar

Slotnick Schacter (2004) Nature Neuroscience

True recognition > False recognition

Old-hits > Related-false alarms

Related-false alarms > Old-hits

Ventral View

LH

Early visual regions (BA17, BA18)

Time (sec)

% S

igna

l cha

nge

00.10.20.3

-0.1-0.2-0.3

0 4 8 12 16

Left fusiform gyrus (BA18)

Old-hitsRelated-false alarms

X

LH

Old-hits > Old-misses

Old-hits + Old-misses

Nature of visual area activity?

* Old-hits > Old-misses should reflect conscious recollection

Time (sec)

% S

igna

l cha

nge

00.10.2

-0.1-0.2

0 4 8 12 16

Left fusiform gyrus (BA37)

Old-hitsOld-missesNew-correct rejections

Late visual regions (BA19, BA37)

* Old-hits + Old-misses expected to reflect nonconscious activity

Time (sec)

% S

igna

l cha

nge

0

0.2

-0.2

0 4 8 12 16

Left cuneus (BA18)

0.4

Early visual regions (BA17, BA18)

Ventral View

Line Orientation Task*For each shape (at ‘study’ or ‘test’), speeded

response whether internal lines sloped:

1) upward

2) downward

*Subjects were not informed that any shapes would be repeated.

Line Judgment Task: Old>Related

Ventral View

* Early visual regions (BA17, BA18)

Old > Related

Related > OldX

LH

Left lingual gyrus (BA18)

Time (sec)

% S

igna

l cha

nge

0

0.1

-0.1

0 4 8 12 16

OldRelated

0.2

* No late visual region activity (BA19,BA37)

Slotnick & Schacter (2006) Neuropsychologia

Line Judgment Task: Behavioral Results

Old Related New

Rea

ctio

n T

ime

(ms)

910

920

930

940

950

960

970

980

ns

* p < 0.05

**

Slotnick & Schacter (2006) Neuropsychologia

A

D

A

Stimulus Specificity

MostLeast

LR

Schacter, Wig & Stevens (2007). Curr Opin Neurobiol

A multiple component model of priming

-Amodal

-Priming across abstract representations

-Sensitive to changes in stimulus-decision mapping

-Most consistently correlated with behavior