Interhemispheric differences of spectral power in expressive language: a MEG study with clinical applications.
In the last decade we have seen an exponential growth of functional imaging studies investigating multiple aspects of language processing. These studies have sparked an interest in applying some of the paradigms to various clinically relevant questions, such as the identification of the cortical regions mediating language function in surgical candidates for refractory epilepsy. Here we present data from a group of adult control participants in order to investigate the potential of using frequency specific spectral power changes in MEG activation patterns to establish lateralisation of language function using expressive language tasks. In addition, we report on a paediatric patient whose language function was assessed before and after a left hemisphere amygdalo-hippocampectomy. Our verb generation task produced left hemisphere decreases in beta-band power accompanied by right hemisphere increases in low beta-band power in the majority of the control group, a previously unreported phenomenon. This pattern of spectral power was also found in the patient's post-surgery data, though not her pre-surgery data. Comparison of pre and post-operative results also provided some evidence of reorganisation in language related cortex both inter- and intra-hemispherically following surgery. The differences were not limited to changes in localisation of language specific cortex but also changes in the spectral and temporal profile of frontal brain regions during verb generation. While further investigation is required to establish concordance with invasive measures, our data suggest that the methods described may serve as a reliable lateralisation marker for clinical assessment. Furthermore, our findings highlight the potential utility of MEG for the investigation of cortical language functioning in both healthy development and pathology.
Fisher
Alison Eleanor
AE
Neuroscience Research, School of Life and Health Sciences, Aston University, Birmingham, B4 7ET, United Kingdom.
Furlong
Paul Lawrence
PL
Seri
Stefano
S
Adjamian
Peyman
P
Witton
Caroline
C
Baldeweg
Torsten
T
Phillips
Sunny
S
Walsh
Richard
R
Houghton
Judith M
JM
Thai
Ngoc Jade
NJ
D000328:Adult; D000679:Amygdala / Q000601:surgery; D001611:Beta Rhythm; D016022:Case-Control Studies; D004292:Dominance, Cerebral / Q000502:physiology*; D004827:Epilepsy / Q000175:diagnosis / Q000503:physiopathology* / Q000601:surgery; D005260:Female; D006624:Hippocampus / Q000601:surgery; D006801:Humans; D007802:Language; D015225:Magnetoencephalography; D008297:Male; D008875:Middle Aged; D012016:Reference Values; D014705:Verbal Behavior / Q000502:physiology*; D014706:Verbal Learning / Q000502:physiology; D014936:Word Association Tests