Significant brain activation associated with the production of /a/ in younger individuals (A), /pataka/ in younger individuals (B), /a/ in older individuals (C), and /pataka/ in older individuals (D), vs. baseline.

Sörös P, Bose A, Sokoloff LG, Graham SJ, Stuss DT. Age-related changes in the functional neuroanatomy of overt speech production. Neurobiol Aging. 2009 (in print). PubMed | PDF

Abstract
Alterations of existing neural networks during healthy aging, resulting in behavioral deficits and changes in brain activity, have been described for cognitive, motor, and sensory functions. To investigate age-related changes in the neural circuitry underlying overt non-lexical speech production, functional MRI was performed in 14 healthy younger (21-32 years) and 14 healthy older individuals (62-84 years). The experimental task involved the acoustically cued overt production of the vowel /a/ and the polysyllabic utterance /pataka/. In younger and older individuals, overt speech production was associated with the activation of a widespread articulo-phonological network, including the primary motor cortex, the supplementary motor area, the cingulate motor areas, and the posterior superior temporal cortex, similar in the /a/ and /pataka/ condition. An analysis of variance with the factors age and condition revealed a significant main effect of age. Irrespective of the experimental condition, significantly greater activation was found in the bilateral posterior superior temporal cortex, the posterior temporal plane, and the transverse temporal gyri in younger compared to older individuals. Significantly greater activation was found in the bilateral middle temporal gyri, medial frontal gyri, middle frontal gyri, and inferior frontal gyri in older vs. younger individuals. The analysis of variance did not reveal a significant main effect of condition and no significant interaction of age and condition. These results suggest a complex reorganization of neural networks dedicated to the production of speech during healthy aging.

Presentation
Sörös P. Changes of Brain Function in Healthy Aging. Presentation at the Geriatrics Conference, University of South Carolina School of Medicine, Division of Geriatrics, Columbia, SC (2010). PDF

MEG recordings during rapid auditory stimulation in younger (upper graph) and older adults

Sörös P, Teismann IK, Manemann E, Lütkenhöner B. Auditory temporal processing in healthy aging: a magnetoencephalographic study. BMC Neuroscience 2009. PubMed | PDF

The findings of the present MEG study do not provide evidence for the hypothesis that auditory temporal processing, as measured by the decrement (short-term habituation) of the major auditory evoked component, the N1m wave, is impaired in aging. Significantly larger amplitudes of the P1m and N1m waves suggest that the cortical processing of individual sounds differs between younger and older individuals. This result adds to the growing evidence that brain functions, such as sensory processing, motor control and cognitive processing, can change during healthy aging, presumably due to experience-dependent neuroplastic mechanisms.

Presentations
Sörös P. The auditory short-term decrement: characteristics and interindividual variability. Presentation at the Rotman Research Institute, Toronto, Ontario, Canada (2002). PDF

Sörös P. Age-related changes in cortical auditory processing. Presentation at the University of Western Ontario, London, Ontario, Canada (2007). PDF

Sörös P. Changes of Brain Function in Healthy Aging. Presentation at the Geriatrics Conference, University of South Carolina School of Medicine, Division of Geriatrics, Columbia, SC (2010). PDF

ALE image of water swallowing-related brain activity

Sörös P, Inamoto Y, Martin RE. Functional brain imaging of swallowing: An activation likelihood estimation meta-analysis. Hum Brain Mapp 2009. PubMed | PDF

This paper presents the first quantitative voxel-wise meta-analysis of swallowing-related brain function. Data analysis was performed with the activation likelihood estimation (ALE) approach, using the freely available software GingerALE.

Abstract
A quantitative, voxel-wise meta-analysis was performed to investigate the cortical control of water and saliva swallowing. Studies that were included in the meta-analysis (1) examined water swallowing, saliva swallowing, or both, and (2) reported brain activation as coordinates in standard space. Using these criteria, a systematic literature search identified seven studies that examined water swallowing and five studies of saliva swallowing. An activation likelihood estimation (ALE) meta-analysis of these studies was performed with GingerALE. For water swallowing, clusters with high activation likelihood were found in the bilateral sensorimotor cortex, right inferior parietal lobule, and right anterior insula. For saliva swallowing, clusters with high activation likelihood were found in the left sensorimotor cortex, right motor cortex, and bilateral cingulate gyrus. A between-condition meta-analysis revealed clusters with higher activation likelihood for water than for saliva swallowing in the right inferior parietal lobule, right postcentral gyrus, and right anterior insula. Clusters with higher activation likelihood for saliva than for water swallowing were found in the bilateral supplementary motor area, bilateral anterior cingulate gyrus, and bilateral precentral gyrus. This meta-analysis emphasizes the distributed and partly overlapping cortical networks involved in the control of water and saliva swallowing. Water swallowing is associated with right inferior parietal activation, likely reflecting the sensory processing of intraoral water stimulation. Saliva swallowing more strongly involves premotor areas, which are crucial for the initiation and control of movements.

Poster
This study was presented as a poster at the 53rd annual meeting of the German Society for Neurophysiology and Functional Imaging, Munich, Germany. PDF

Swallowing
Martin RE, MacIntosh BJ, Smith RC, Barr AM, Stevens TK, Gati JS, Menon RS. Cerebral areas processing swallowing and tongue movement are overlapping but distinct: a functional magnetic resonance imaging study. J Neurophysiol. 2004;92:2428-43 PubMed | PDF

Martin RE, Goodyear BG, Gati JS, Menon RS. Cerebral cortical representation of automatic and volitional swallowing in humans. J Neurophysiol. 2001;85:938-50. PubMed | PDF

Meta-analysis
For an introduction in quantitative meta-analyses see the paper of Laird et al. HBM 2005. A selection of papers using GingerALE can be found here.

Background: Although the posterior oral cavity and oropharynx play a major role in swallowing, their central representation is poorly understood.

Methods: High-field functional magnetic resonance imaging of the brain was used to study the central processing of brief air-pulses, delivered to the peritonsillar region of the lateral oropharynx, in 6 healthy adults.

Results: Bilateral air-pulse stimulation was associated with the activation of a bilateral network including the primary somatosensory cortex and the thalamus, classical motor areas (primary motor cortex, supplementary motor area, cingulate motor areas), and polymodal areas (including the insula and frontal cortex).

Conclusions: These results suggest that oropharyngeal stimulation can activate a bilaterally distributed cortical network that overlaps cortical regions previously implicated in oral and pharyngeal sensorimotor functions such as tongue movement, mastication, and swallowing. The present study also demonstrates the utility of air-pulse stimulation in investigating oropharyngeal sensorimotor processing in functional brain imaging experiments.

A more detailed description of this study can be found here.

The following oral presentation, given at the Dysphagia Research Society 2008 in Charleston, SC, USA, presents a study on somatosensory processing of brief air-pulse stimuli. A more detailed description of this study can be found here.

Sörös P, Lalone E, Smith R, Stevens T, Theurer J, Menon R, Martin R. Functional MRI of oropharyngeal air-pulse stimulation. Download

A second talk presented the results of a quantitative, voxel-wise meta-analysis of swallowing-related brain activity in humans, based on fMRI, PET, and MEG studies.

Sörös P, Inamoto Y, Martin R. Functional brain imaging of swallowing: An activation likelihood meta-analysis. Download

Aim: We tested the hypothesis that reduced nutritional status or the degree of tissue catabolism are associated with the presence of hepatic encephalopathy in 223 patients with histologically confirmed non-alcoholic cirrhosis.
Results: Nutritional status and tissue catabolism were not significantly different between patients with and without hepatic encephalopathy.
Conclusions: Our data do not support the hypothesis that malnutrition or tissue catabolism are independent risk factors for the presence of hepatic encephalopathy in patients with non-alcoholic cirrhosis.

Background. To characterise the neural correlates of intact vibrotactile working memory and attention, we conducted functional MRI in 12 healthy young adults. Participants performed a forced-choice vibrotactile frequency discrimination task, comparing a cue stimulus of fixed frequency to their right thumb with a probe stimulus of identical or higher frequency. To investigate working memory, the time interval between the 2 stimuli was pseudo-randomised (either 2 or 8 s). To investigate selective attention, a distractor stimulus was occasionally presented contralaterally, simultaneous to the probe.

Results. Delayed vibrotactile frequency discrimination, following a probe presented 8 s after the cue in contrast to a probe presented 2 s after the cue, was associated with activation in the bilateral anterior insula and the right inferior parietal cortex. Frequency discrimination under distraction was correlated with activation in the right anterior insula, in the bilateral posterior parietal cortex, and in the right middle temporal gyrus.

Conclusions. These results support the notion that working memory and attention are organised in partly overlapping neural circuits. In contrast to previous reports in the visual or auditory domain, this study emphasises the involvement of the anterior insula in vibrotactile working memory and selective attention. ]]> http://neuroactivity.org/2007/07/18/fmri-of-vibrotactile-processing/feed/ http://neuroactivity.org/2007/03/18/functional-imaging-of-speech-production/ http://neuroactivity.org/2007/03/18/functional-imaging-of-speech-production/#comments Sun, 18 Mar 2007 11:49:55 +0000 Peter Soros http://neuroactivity.org/2007/03/18/functional-imaging-of-speech-production/

This is a presentation I gave at the Ontario Aphasia Interest Group Teleconference in December 2006. It summarizes the findings of my fMRI study on speech production in healthy younger adults (Neuroimage 2006;32(1):376-387). The presentation is available as Flash web presentation or as a pdf (6 MB).

Abstract
A combination of magnetoencephalography and proton magnetic resonance spectroscopy was used to correlate the electrophysiology of rapid auditory processing and the neurochemistry of the auditory cortex in 15 healthy adults. To assess rapid auditory processing in the left auditory cortex, the amplitude and decrement of the N1m peak, the major component of the late auditory evoked response, were measured during rapidly successive presentation of acoustic stimuli. We tested the hypothesis that: (i) the amplitude of the N1m response and (ii) its decrement during rapid stimulation are associated with the cortical neurochemistry as determined by proton magnetic resonance spectroscopy.

Results. Our results demonstrated a significant association between the concentrations of N-acetylaspartate, a marker of neuronal integrity, and the amplitudes of individual N1m responses. In addition, the concentrations of choline-containing compounds, representing the functional integrity of membranes, were significantly associated with N1m amplitudes. No significant association was found between the concentrations of the glutamate/glutamine pool and the amplitudes of the first N1m. No significant associations were seen between the decrement of the N1m (the relative amplitude of the second N1m peak) and the concentrations of N-acetylaspartate, choline-containing compounds, or the glutamate/glutamine pool. However, there was a trend for higher glutamate/glutamine concentrations in individuals with higher relative N1m amplitude.

Conclusion. These results suggest that neuronal and membrane functions are important for rapid auditory processing. This investigation provides a first link between the electrophysiology, as recorded by magnetoencephalography, and the neurochemistry, as assessed by proton magnetic resonance spectroscopy, of the auditory cortex.

Sörös P, Dziewas R, Manemann E, Teismann IK, Lütkenhöner B. No indication of brain reorganization after unilateral ischemic lesions of the auditory cortex. Neurology 2006;67:1059-1061 PubMed Reprint

Abstract
We used magnetoencephalography to study contralesional auditory reorganization in three men with chronic unilateral ischemic lesions of the auditory cortex. While no response was found over the lesioned hemisphere, processing in the unaffected hemisphere was indistinguishable vs. healthy controls. In contrast to sensorimotor and language systems, the auditory system appears to lack contralateral reorganization, presumably because patients are typically not aware of hearing deficits and thus do not perform training.