Visual discrimination after anterior temporal lobectomy in humans.
OBJECTIVE
To determine whether right anterior temporal lobectomy (RTL) results in perceptual deficits, and whether the perception of particular stimulus features (i.e., shape, motion, color) is affected differentially.


BACKGROUND
RTL results in abnormal visual discrimination, recognition, and recall of pictorial material that cannot be easily specified verbally, such as designs and faces. It is unclear whether stimuli must be conceptually meaningful to elicit perceptual deficits.


METHODS
Tests were constructed to assess a wide spectrum of basic visual discrimination abilities with simple, meaningless stimuli. The performance of nine patients who underwent left temporal lobectomy (LTL) and nine patients who underwent RTL were compared with that of normal control individuals. The mean excision size along lateral cortex was 3.7 cm for the LTL group and 5.6 cm for the RTL group; mean mesial excision size was 5.2 cm for LTL and 4.6 cm for RTL.


RESULTS
Basic visual discrimination capacities were demonstrated to be essentially intact after LTL and RTL, except for a mild loss of blue color discrimination after RTL.


CONCLUSIONS
There is little evidence that RTL produces perceptual impairments limited to the domain of pattern perception, or generalizable to nonmeaningful stimuli. The perceptual loss after RTL may be largely restricted to extraction of meaning, and related to the disruption of the circuits that connect the outcome of visual analysis to previously stored semantic information.
Mendola
J D
JD
Department of Brain and Cognitive Sciences and the Clinical Research Center, Massachusetts Institute of Technology, Cambridge, USA.
Rizzo
J F
JF
Cosgrove
G R
GR
Cole
A J
AJ
Black
P
P
Corkin
S
S
D000328:Adult; D004192:Discrimination, Psychological / Q000502:physiology*; D004827:Epilepsy / Q000503:physiopathology; D005260:Female; D006801:Humans; D008297:Male; D010364:Pattern Recognition, Visual; D013647:Task Performance and Analysis; D013702:Temporal Lobe / Q000503:physiopathology / Q000601:surgery*; D014796:Visual Perception / Q000502:physiology*