Imageability Effects on Sentence Judgments by

Right Brain-Damaged Adults

Lisa G. Lederer 1, April Gibbs Scott 1, Connie A. Tompkins1,2, Michael W. Dickey 1

1.University of Pittsburgh; 2. Center for the Neural Basis of CognitionPittsburgh, P.A. USA

INTRODUCTION & INTRODUCTION & OVERVIEWOVERVIEW

• Image generation has often been assumed to be a right hemisphere function.

• Many recent studies, however, have localized image generation to the posterior left hemisphere (see Farah, 1995, for a review).

• This study sought to clarify the relationship between right hemisphere damage (RHD) and image-generation ability using a stimulus set developed by Eddy and Glass (1981).

• The performance of adults with and without RHD was compared on true/false items whose solution did or did not require imagery generation.

PARTICIPANTSPARTICIPANTS

• 34 adults with unilateral RHD (confirmed by CT or MRI) due to CVA

• 38 healthy controls• Monolingual native speakers of American English• Pre-morbid right-handedness• RHD’s performed significantly poorer than healthy control group

on:• Peabody Picture Vocabulary Test-Revised (Dunn & Dunn, 1997)

• Behavioural Inattention Test (Wilson, Cockburn, & Halligan, 1987)

• Visual Form Discrimination (Benton, Sivan, Hamsher, Varney, & Spreen, 1994)

• Judgment of Line Orientation (Benton, Hamsher, Varney, & Spreen,1983)

PARTICIPANT PARTICIPANT DEMOGRAPHICSDEMOGRAPHICS

Characteristics                       RHD (n=34)                         NBD (n=38)

Age (years)                                  

  Mean (SD)               64.74 (11.57)                       60.45 (9.61)

Range                     42-85                             45-84  

Gender

Male    17                                        19

Female     17           19

Education (years)

  Mean (SD)              14.42 (2.96)                          13.95 (2.27)      Range               10-22                12-20

Months post-onset            

Mean (SD)              52.91 (50.99) Not applicable

Range                    4-167

STIMULI & PROCEDURESTIMULI & PROCEDURE• 18 High- and 17 Low-imageability sentences, as determined by naïve raters, from Eddy & Glass

(1981) (matched for noun frequency, mean auditory verification RTs, truth agreement, and comprehensibility)

• 36 filler stimuli similar in structure• Participants received extensive orientation and practice until reaction time stabilized• Stimuli presented auditorily via a notebook computer through supra-oral earphones• Participants responded true/false on manual two-button box• Were encouraged to respond as quickly as possible• Completed over 3 sessions• High-imageability sentences classified as motor/visual or visual-only by 3 raters with >

80% inter-rater reliability for post-hoc analysis

 

LOW-IMAGEABLE

• There are six days in a week.• Geology is the study of living

matter.• Middle age comes after old age.• The best student is at the

bottom of the class.• A country has windows.• There are three human sexes.• Spring is a month.• A novel is shorter than a

novelette.• The introduction follows the

story.

• Salt is used less often than pepper.

• The prince will one day be queen.

• A pound is heavier than a ton.• Most watchdogs are Bulldogs.• Animals are stuffed by a

toxicologist.• Geology studies the history of

mankind.• A father buys children.• The US government functions

under a three party system.

HIGH-IMAGEABLE

• A row boat comes to a point in the back.

• The symbol for degrees is an apostrophe.

• Yellow is darker than orange.• A grapefruit is larger than a

cantaloupe.• A stop sign has seven sides.• Tractors have two very large

wheels in front.

• The letter A is formed with four lines.

• The number 9 can be constructed from two circles.

• The hot water handle on a sink is on the right.

• A right handed hitter places his right side toward the plate.

• The accelerator on a car is on the left pedal.

VISUAL ONLY MOTOR/VISUAL

RESULTSRESULTSGeneral Analysis (Two-way ANOVA)

• Both groups more accurate on Low- than on High- imageable items (F(1, 71) = 25.02, p < .001)

• RHD group less accurate than NBD in general

(F(1, 70) = 6.40, p =.014)• Group x Imagery interaction in RT (F(1, 63) = 5.42, p = .023)• NBD group  faster on Low- than High-imageable items (t(33) =

2.44, p =.020). No difference between High and Low items for RHD group (t(30)=1.00, p = .325, ns)

Post-hoc Imagery Type Analysis• Group x High Imagery type accuracy interaction

(F(1, 70) = 5.71, p =.02)• RHD group less accurate than NBD on visual/motor items• No group difference on visual-only items

RESULTSRESULTS

RESULTS

DISCUSSIONDISCUSSION• Differences in RT between stimulus sets (high vs. low imageable)

were only seen for the NBD group.

• Not due to a speed-accuracy tradeoff or to syntactic differences between stimulus sets (per correlation analyses)

• Suggests that RHD disproportionately slows access to “world” knowledge as opposed to imagery-based knowledge.

• Consistent with Farah (1995) and others’ assertion that image generation primarily involves the left hemisphere

FURTHER DISCUSSION & FURTHER DISCUSSION & IMPLICATIONSIMPLICATIONS

• Post-hoc analysis of visual-only vs. visual/motor imagery suggests that this relative sparing of visual imagery generation does not extend to motor imagery.

• Adults with RHD might rely disproportionately on visual imagery generation processes but not on motor imagery generation processes.

• Researchers should consider the distinction between visual imagery and motor imagery generation.

• Clinicians should attempt even more fine-grained analysis (i.e. less coarse than “visual imagery generation” and “motor imagery generation”) of clients’ problem areas.

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Benton, A. L., Sivan, A. B., Hamsher, K. d., Varney, N. R., & Spreen, O. (1994). Visual Form Discrimination. In Contributions to Neuropsychological Assessment (2nd ed.), (pp. 65-72). New York: Oxford University Press.

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Wilson, B., Cockburn, J., & Halligan, P. (1987). Behavioural Inattention Test. Titchfield, England: Thames Valley Test Company.