Altered patterns of cortical activation in ALS patients during attention and cognitive response inhibition tasks

Abstract

Since amyotrophic lateral sclerosis (ALS) can be accompanied by executive dysfunction, it is hypothesised that ALS patients will have impaired performance on tests of cognitive inhibition. We predicted that ALS patients would show patterns of abnormal activation in extramotor regions when performing tests requiring the inhibition of prepotent responses (the Stroop effect) and the inhibition of prior negatively primed responses (the negative priming effect) when compared to healthy controls. Functional magnetic resonance imaging was used to measure activation during a sparse sequence block design paradigm investigating the Stroop and negative priming effects in 14 ALS patients and 8 healthy age- and IQ-matched controls. Behavioural measures of performance were collected. Both groups' reaction times (RTs) reflected the Stroop effect during scanning. The ALS and control groups did not differ significantly for any of the behavioural measures but did show significant differences in cerebral activation during both tasks. The ALS group showed increased activation predominantly in the left middle temporal gyrus (BA 20/21), left superior temporal gyrus (BA 22) and left anterior cingulate gyrus (BA 32). Neither group's RT data showed clear evidence of a negative priming effect. However the ALS group showed decreased activation, relative to controls, particularly in the left cingulate gyrus (BA 23/24), left precentral gyrus (BA 4/6) and left medial frontal gyrus (BA 6). Greater cerebral activation in the ALS group accompanying the performance of the Stroop effect and areas of decreased activation during the negative priming comparison suggest altered inhibitory processing in ALS, consistent with other evidence of executive dysfunction in ALS. The current findings require further exploration in a larger study.

Fig. 1

Brain regions differentially activated in the ALS and healthy control groups during the Stroop minus Control conditions (i.e. the Stroop effect) at p = 0.001. All regions demonstrating significant between-group activation differences (shown in red) showed increased activation in the ALS group relative to healthy controls. No areas of decreased activation in the ALS group relative to controls were observed

Fig. 2

Brain regions differentially activated in the ALS and healthy control groups during the negative priming minus Stroop conditions (negative priming effect) at p = 0.001. All regions demonstrating significant between-group activation (shown in blue) showed decreased activation in the ALS group relative to healthy controls. No areas of increased activation in the ALS group relative to controls were observed