Research aims and technics in our team

Our research aims are to reveal neural basis of pathological features of sensory and motor processing disorders (ASD) using psychophysics and neuroscientific technics. In our team, we use interdisciplinary approach for this problem and are attempting to build clinical application in collaborating especially with occupational therapists based on neuroscientific evidences. We employ psychophysics and neuroscientific technics for this goal.

Studies in sensory processing disorders

Individuals with ASD have been reported to have sensory processing disorders at about 90 - 96 %. The disorders are defined in clinical research field as to be constructed by four categories, 1) sensory sensitivity, 2) sensory avoiding, 3) low registration and 4) sensation seeking. Former two components (i.e., sensory sensitivity and sensory avoiding) relate extraordinary strong perceptual impletion for sensory stimuli and the degree to escape such the stimuli. Later two (i.e., low registration and sensation seeking) relate lower perceptual impletion of stimuli which sometimes resulting in high risks not to escape dangerous situations and rather approach the situations.

 

We aim to reveal neural basis of sensory processing disorders using psychophysics and neuroscientific technics. We especially sought to elucidate that highly excited condition in the cerebral cortex resulting from abnormal gamma-aminobutyric acid (GABA) concentration engage with enhanced perceptual function observed in individuals with ASD. Many studies have been reported that excitation and inhibition imbalance (E/I imbalance) is a representative character of the autistic brain, which is based on abnormal metabolism of GABA that is an inhibitory neurotransmitter in the brain. In order to reveal how this condition would contribute characteristic perceptual function of ASD, we employ functional MRI (fMRI) and MRspectroscopy (MRS). We study underlying neural basis of association between prominent perceptual function and reduced GABA concentration using these technics.

 

Our study (Ide et al., 2019) an association of temporal resolution of tactile stimuli and severity of sensory hyper-reactivity. We employed temporal order judgement (TOJ) task which participants are requested to judge the orders of two successive vibrotactile stimuli which were divided in temporal lags of 15 ms ～ 240 ms. The result demonstrated that if ASD participants have high temporal resolution (i.e., they precisely the order if the gaps were very short), they tended to have severer sensory hyper-reactivity. This relationship was found only in ASD group but not typically developing group. We also reported that the severity of sensor hyper-reactivity is linked to lower GABA concentration in ventral premotor cortex (vPMC) (Umesawa et al., 2020). vPMC was found as an neural correlates of prominent temporal resolution since an ASD patient who correctly performed TOJ even if temporal lags was 6.5 ms (this performance was about 10 times greater than average of control group) exhibited higher neural activity in this brain area when performing TOJ (Ide et al., 2020). These findings demonstrated that there are shared neural substrates between temporal processing of sensory inputs and sensory hyper-reactivity in ASD.

 

Refereces

• Umesawa Y*, Atsumi T*, Chakrabarty M, Fukatsu R, Ide M. (2020) GABA concentration in the left ventral premotor cortex associates with sensory hyper-responsiveness in autism spectrum disorders without intellectual disability.Frontiers in Neuroscience.14,482.website
• Ide M*, Atsumi T*, Chakrabarty M*, Yaguchi A, Umesawa Y, Fukatsu R & Wada M. (2020) Neural basis of extremely high temporal sensitivity: Insights from a patient with autism. Frontiers in Neuroscience.14,340 [*co-first authors]website
• Ide, M*, Yaguchi, A, Sano, M, Fukatsu, R & Wada, M (2019) Higher tactile temporal resolution as a basis of hypersensitivity in individuals with autism spectrum disorder.Journal of Autism and Delopmental Disorders,49(1), pp44-53.website

Studies in motor disabilities

Developmental coordination disorders (DSD) have been reported to highly comorbid with ASD approximately in 80 % (Green et al., 2018). The features of DCD exhibit quite broad characters of motor difficulties, for instance, to precisely manipulate their fingers, to rhythmically move upper and lower limbs to be coordinated way.

Cortical GABA conditions are also fundamentally engaged with these precisely and synchronously body movements. We reported that reduced GABA concentration in the supplementary motor area (SMA) measured using MRS was associated with lower performance of coordinated movements which were estimated using a clinical assessments BOT-2 (Bruininks-Oseretsky Test of Motor Proficiency | Second Edition). Furthermore, lower performances of gross motor movements were related with higher GABA concentration in primary motor area (M1).

We are now studying the detail kinematical characteristics of motor disabilities of ASD using motion capture systems and psychophysics technics. We aim to elucidate neural basis of the difficulty and develop effective clinical intervention and assessments based on neuroscientific findings.

 

References

• Umesawa Y*, Matsushima K, Atsumi T, Kato T, Fukatsu R, Wada M & Ide M*. (2020) Altered GABA concentration in brain motor area is associated with the severity of motor disabilities in individuals with autism spectrum disorder,Journal of Autism and Developmental Disorders.website