ABSTRACT
Contents Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 498 23.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 499
23.1.1 Theoretical models of autism . . . . . . . . . . . . . . . . . . . . 499 23.2 Minicolumnar neuropathology model of autism and EEG
gamma . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 500 23.3 Functional signicance of gamma oscillations: General
considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 401 23.4 Review of gamma activity ndings in autism . . . . . . . . . . . . . 502
23.4.1 Spontaneous, resting EEG gamma in autism . . . . . . . . 502
Abstract Autism spectrum disorder (ASD) is characterized by severe disturbances in reciprocal social relations; varying degrees of language and communication difculty; and restricted, repetitive, and stereotyped behavioral patterns. Additionally, another frequent symptom of ASD is decient executive functioning. Our group have proposed that supernumerary minicolumns and reduced cell size of pyramidal cells bias corticocortical connections in favor of short projections at the expense of longer commissural ones. Furthermore, the abnormal width of minicolumns in autism reects primarily a loss of the inhibitory tone of anatomical elements surrounding this modular structure. It is proposed that this may result in higher excitation/inhibition ratio in autism. Majority of electroencephalographic (EEG) studies presented ndings of atypical resting-state oscillatory activity and abnormality of both evoked and induced responses in the gamma frequency range in children with ASD, suggesting that high-frequency oscillation anomalies are of possible clinical relevance, and support an imbalance of neural excitation/ inhibition as a potential ASD biomarker. Preliminary evidence suggests that ASD may be associated with changes in gamma-band oscillations. We proposed to use repetitive transcranial magnetic stimulation (rTMS) that has been suggested as a therapeutic attempt at overcoming lateral inhibitory minicolumnar decits. In this chapter, we describe this method of neurotherapy in autism treatment and EEG methods aimed at the assessment of functional changes following rTMS-based neuromodulation. The approach is meant to target the investigation of rTMS-induced positive changes in electrophysiological activity (i.e., quantitative EEG and event-related potentials [ERPs] shown in our preliminary results) and to improve prefrontal executive functions in ASD patients. The chapter will examine the effects of 6, 12, and 18 sessions of low-frequency rTMS bilaterally over the dorsolateral prefrontal cortex (DLPFC) and post-TMS neurofeedback training on behavior, cognitive functions, and other behavioral clinical outcomes in children with autism with the main focus on changes in evoked and induced gamma oscillations.
