Object naming is a more sensitive measure of speech localization than number counting: Converging evidence from direct cortical stimulation and fMRI
Nicole Petrovich Brennan, Stephen Whalen, Daniel M. Branco, James P. O’Shea, Isaiah H. Norton, Alexandra J. Golby
Using direct cortical stimulation to map language function during
awake craniotomy is a well-described and useful technique. However,
the optimum neuropsychological tasks to use have not been detailed.
We used both functional MRI (fMRI) and direct cortical stimulation to
compare the sensitivity of two behavioral paradigms, number counting
and object naming, in the demonstration of eloquent cortical language
areas. Fifteen patients with left hemisphere lesions and seven healthy
control subjects participated. Patients had both preoperative fMRI at
3 T and direct cortical stimulation. Patients and controls performed
object naming and number counting during fMRI at 3 T. Laterality
indices were calculated from the fMRI maps for the Numbercounting >
Object-naming and Object-naming>Number-counting
contrasts. The same number-counting and object-naming paradigms
were tested during awake craniotomy and assessed for sensitivity to
speech disruption. In all patients during intraoperative cortical
stimulation, speech disruption occurred at more sites during object
naming than during number counting. Subtle speech errors were only
elicited with the object-naming paradigm, whereas only speech arrest
and/or hypophonia were measured using the number counting
paradigm. In both patients and controls, fMRI activation maps
demonstrated greater left lateralization for object naming as compared
to number counting in both frontal and temporal language areas.
Number counting resulted in a more bihemispheric distribution of
activations than object naming. Both cortical stimulation testing and
fMRI suggest that automated speech tasks such as number counting
may not fully engage putative language networks and therefore are not
optimal for language localization for surgical planning.
fMRI results for patients and healthy control subjects. fMRI activity lateralizes more completely to the left-hemisphere in the Object-naming < Numbercounting
contrast than the Number-counting > Object-naming contrast in both Broca's and Wernicke's areas. Analyses are random effects group analyses at p<0.01.
Object naming is a more sensitive measure of speech localization than number counting: Converging evidence from direct cortical stimulation and fMRI
Nicole Petrovich Brennan, Stephen Whalen, Daniel M. Branco, James P. O’Shea, Isaiah H. Norton, Alexandra J. Golby
Neuroimage
2007; 37, S100-S108.