title: Evaluating reverse speech as a control task with language-related gamma activity on electrocorticography.
abstract: Reverse speech has often been used as a control task in brain-mapping studies of language utilizing various non-invasive modalities. The rationale is that reverse speech is comparable to forward speech in terms of auditory characteristics, while omitting the linguistic components. Thus, it may control for non-language auditory functions. This finds some support in fMRI studies indicating that reverse speech resulted in less blood-oxygen-level-dependent (BOLD) signal intensity in perisylvian regions than forward speech. We attempted to externally validate a reverse speech control task using intracranial electrocorticography (ECoG) in eight patients with intractable focal epilepsy. We studied adolescent and adult patients who underwent extraoperative ECoG prior to resective epilepsy surgery. All patients received an auditory language task during ECoG recording. Patients were presented 115 audible question stimuli, including 30 reverse speech trials. Reverse speech trials more strongly engaged bilateral superior temporal sites than did the corresponding forward speech trials. Forward speech trials elicited larger gamma-augmentation at frontal lobe sites not attributable to sensorimotor function. Other temporal and frontal sites of significant augmentation showed no significant difference between reverse and forward speech. Thus, we failed to validate reported evidence of weaker activation of temporal neocortices during reverse compared to forward speech. Superior temporal lobe engagement may indicate increased attention to reverse speech. Reverse speech does not appear to be a suitable task for the control of non-language auditory functions on ECoG.
authors.affiliation: MD-PhD Program, School of Medicine, Wayne State University, Detroit, MI 48201, USA.
authors.forename: Erik C
authors.initials: EC
authors.lastname: Brown
authors.forename: Otto
authors.initials: O
authors.lastname: Muzik
authors.forename: Robert
authors.initials: R
authors.lastname: Rothermel
authors.forename: Naoyuki
authors.initials: N
authors.lastname: Matsuzaki
authors.forename: Csaba
authors.initials: C
authors.lastname: Juhász
authors.forename: Aashit K
authors.initials: AK
authors.lastname: Shah
authors.forename: Marie D
authors.initials: MD
authors.lastname: Atkinson
authors.forename: Darren
authors.initials: D
authors.lastname: Fuerst
authors.forename: Sandeep
authors.initials: S
authors.lastname: Mittal
authors.forename: Sandeep
authors.initials: S
authors.lastname: Sood
authors.forename: Vaibhav A
authors.initials: VA
authors.lastname: Diwadkar
authors.forename: Eishi
authors.initials: E
authors.lastname: Asano
mesh_terms: D000293:Adolescent; D000328:Adult; D001307:Auditory Perception / Q000502:physiology*; D001921:Brain / Q000502:physiology*; D001931:Brain Mapping / Q000379:methods*; D002648:Child; D004569:Electroencephalography; D005260:Female; D006801:Humans; D007802:Language; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D013060:Speech; D055815:Young Adult