Motor cortical excitability and pre‐supplementary motor area neurochemistry in healthy adults with substantia nigra hyperechogenicity. Issue 2 (10th November 2022)

• Record Type: Journal Article
• Authors: Todd, Gabrielle; Rae, Caroline D.; Taylor, Janet L.; Rogasch, Nigel C.; Butler, Jane E.; Hayes, Michael; Wilcox, Robert A.; Gandevia, Simon C.; Aoun, Karl; Esterman, Adrian; Lewis, Simon J. G.; Hall, Julie M.; Matar, Elie; Godau, Jana; Berg, Daniela; Plewnia, Christian; von Thaler, Anna‐Katharina; Chiang, Clarence; Double, Kay L.
• Is Part Of: Journal of neuroscience research. Volume 101:Issue 2(2023)
• Page Start: 263
• Page End: 277
• Publication Date: 2022-11-10
• Subjects: motor cortex -- pre‐supplementary motor area -- substantia nigra -- transcranial magnetic stimulation; Neurobiology -- Periodicals; 612
• DOI: 10.1002/jnr.25145
• Languages: English
• ISSNs: 0360-4012

Abstract

Abstract: Substantia nigra (SN) hyperechogenicity, viewed with transcranial ultrasound, is a risk marker for Parkinson's disease. We hypothesized that SN hyperechogenicity in healthy adults aged 50–70 years is associated with reduced short‐interval intracortical inhibition in primary motor cortex, and that the reduced intracortical inhibition is associated with neurochemical markers of activity in the pre‐supplementary motor area (pre‐SMA). Short‐interval intracortical inhibition and intracortical facilitation in primary motor cortex was assessed with paired‐pulse transcranial magnetic stimulation in 23 healthy adults with normal ( n = 14; 61 ± 7 yrs) or abnormally enlarged (hyperechogenic; n = 9; 60 ± 6 yrs) area of SN echogenicity. Thirteen of these participants (7 SN− and 6 SN+) also underwent brain magnetic resonance spectroscopy to investigate pre‐SMA neurochemistry. There was no relationship between area of SN echogenicity and short‐interval intracortical inhibition in the ipsilateral primary motor cortex. There was a significant positive relationship, however, between area of echogenicity in the right SN and the magnitude of intracortical facilitation in the right (ipsilateral) primary motor cortex ( p = .005; multivariate regression), evidenced by the amplitude of the conditioned motor evoked potential (MEP) at the 10–12 ms interstimulus interval. This relationship was not present on the left side. Pre‐SMA glutamate did not predict primary motor cortex inhibition or facilitation. The results suggest that SN hyperechogenicity in healthy older adults may be associated with changes in excitability of motor cortical circuitry. The results advance understanding of brain changes in healthy older adults at risk of Parkinson's disease. Abstract : Substantia nigra (SN) hyperechogenicity, viewed with transcranial ultrasound, is a risk marker for Parkinson's disease. SN hyperechogenicity in healthy older adults is associated with changes in the excitability of specific motor cortical circuitry. These changes are unrelated to glutamate levels in the pre‐supplementary motor area (pre‐SMA).