Neural Correlates of Oral Stereognosis-An fMRI Study.

Oral stereognosis is the ability to recognize, discriminate and localize a bolus in the oral cavity. Clinical observation indicates deficits in oral stereognosis in patients with vascular or neurodegenerative diseases particularly affecting the parietal lobes. However, the precise neural representation of oral stereognosis remains unclear whereas the neural network of manual stereognosis has already been identified. We hypothesize that oral and manual stereognosis share common neuronal substrates whilst also showing somatotopic distribution. Functional magnetic resonance images (fMRI; Siemens Prisma 3 T) from 20 healthy right-handed participants (11 female; mean age 25.7 years) using a cross-modal task of oral and manual spatial object manipulation were acquired. Data were analyzed using FSL software using a block design and standard analytical and statistical procedures. A conjunction analysis targeted the common neuronal substrate for stereognosis. Activations associated with manual and oral stereognosis were found in partially overlapping fronto-parietal networks in a somatotopic fashion, where oral stereognosis is located caudally from manual stereognosis. A significant overlap was seen in the left anterior intraparietal sulcus. Additionally, cerebellar activations were shown particularly for the oral condition. Spatial arrangement of shaped boli in the oral cavity is associated with neuronal activity in fronto-parietal networks and the cerebellum. These findings have significant implications for clinical diagnostics and management of patients with lesions or atrophy in parietal lobule (e.g. Alzheimer's disease, stroke). More studies are required to investigate the clinical effect of damage to these areas, such as loss of oral stereognosis or an impaired oral phase.

The efficacy of a directed rhythmic-melodic voice training in the treatment of chronic non-fluent aphasia-Behavioral and imaging results.

The main objective of this study was to investigate the efficacy of a directed rhythmic-melodic voice training (SIPARI) compared to language therapy with the focus on improvement in expressive linguistic performance. 20 patients suffering from chronic non-fluent aphasia, allocated by coin tossing to either of the groups, participated in 32 single therapy sessions over a period of 4 months. Before and after therapy, independent testers performed a standardized language test (Aachener Aphasie Test). Behavioral assessments revealed that improvements of patients of the experimental group were clinically significant compared to those of the control group. These improvements concerned the description level articulation and prosody for spontaneous speech and the subtests repetition, naming, and comprehension. Based on these improvements, a significant increase in profile level (effect size (ES) = 2.028, p < 0.001) was assessed, an overall and clinically relevant measure of the severity of aphasia. Additional fMRI examinations yielded activation in the left superior frontal gyrus for the post-minus pre- therapy assessments only for participants of the experimental group. Since this brain region is reported to be particularly involved in executive processing, we assume that the directed procedure of the SIPARI treatment with regard to musical, linguistic, and cognitive function potentially holds the key for successful language rehabilitation. While our imaging results hint at a possible explanation for its efficacy, our behavioral results corroborate the efficacy of this therapy in the treatment of chronic non-fluent aphasia patients. DRKS00026730, 19.10.21, retrospectively registered https://www.drks.de/drks_web/navigate.do?navigationId=trial.HTML&TRIAL_ID=DRKS00026730.

Excitatory-inhibitory balance within EEG microstates and resting-state fMRI networks: assessed via simultaneous trimodal PET-MR-EEG imaging.

The symbiosis of neuronal activities and glucose energy metabolism is reflected in the generation of functional magnetic resonance imaging (fMRI) and electroencephalography (EEG) signals. However, their association with the balance between neuronal excitation and inhibition (E/I-B), which is closely related to the activities of glutamate and γ-aminobutyric acid (GABA) and the receptor availability (RA) of GABAA and mGluR5, remains unexplored. This research investigates these associations during the resting state (RS) condition using simultaneously recorded PET/MR/EEG (trimodal) data. The trimodal data were acquired from three studies using different radio-tracers such as, [11C]ABP688 (ABP) (N = 9), [11C]Flumazenil (FMZ) (N = 10) and 2-[18F]fluoro-2-deoxy-D-glucose (FDG) (N = 10) targeted to study the mGluR5, GABAA receptors and glucose metabolism respectively. Glucose metabolism and neuroreceptor binding availability (non-displaceable binding potential (BPND)) of GABAA and mGluR5 were found to be significantly higher and closely linked within core resting-state networks (RSNs). The neuronal generators of EEG microstates and the fMRI measures were most tightly associated with the BPND of GABAA relative to mGluR5 BPND and the glucose metabolism, emphasising a predominance of inhibitory processes within in the core RSNs at rest. Changes in the neuroreceptors leading to an altered coupling with glucose metabolism may render the RSNs vulnerable to psychiatric conditions. The paradigm employed here will likely help identify the precise neurobiological mechanisms behind these alterations in fMRI functional connectivity and EEG oscillations, potentially benefitting individualised healthcare treatment measures.