The superior parietal lobule (SPL) plays a strategic role in somatosensory and visuomotor integration. This study aims to evaluate the clinical, neurocognitive, and behavioral characteristics of isolated SPL stroke.

We assessed neuropsychological and behavioral findings in 14 patients with isolated SPL stroke among 4200 patients with ischemic stroke. All patients underwent neuroimaging, clinical and neuropsychological assessment after stroke.

Of the 14 patients enrolled, the first complaints were tactile and visuospatial disorders at stroke onset. Except for 6 patients with only 1 cognitive impairment, the majority of patients (57%) experienced more than 1 cognitive impairment category. Functional hemispheric asymmetries have been found in different cognitive processes, such as between visuospatial and body image functions and language process. Among visuospatial abilities disorders, spatial disorientation, visuospatial neglect, and visual extinction were found in two-thirds (63%) of patients with right SPL lesion. Body schema and image disorders were observed in all patients with right-sided lesions, such as alien hand, autotopagnosia for body parts (36%), autotopagnosia for sensory sensations (36%), and fading limb (21%). Two-thirds (57%) of patients with left SPL had impairment in language abilities.

Our findings after stroke suggest that SPL plays a pivotal role in the regulation of visuospatial abilities, body schema and body image processing, and language skills through bilateral frontoparietal networks and interhemispheric parietal networks.

People with schizophrenia recognize speech poorly under multiple-people-talking (informational masking) conditions. In reverberant environments, direct-wave signals from a speech source are perceptually integrated with the source reflections (the precedence effect), forming perceived spatial separation (PSS) between different sources and consequently improving target-speech recognition against informational masking. However, the brain substrates underlying the schizophrenia-related vulnerability to informational masking and whether schizophrenia affects the unmasking effect of PSS are largely unknown.

Using psychoacoustic testing and functional magnetic resonance imaging, respectively, the speech recognition under either the PSS or perceived spatial co-location (PSC) condition and the underlying brain substrates were examined in 20 patients with schizophrenia and 16 healthy controls.

Speech recognition was worse in patients than controls. Under the PSS (but not PSC) condition, speech recognition was correlated with activation of the superior parietal lobule (SPL), and target speech-induced activation of the SPL, precuneus, middle cingulate cortex and caudate significantly declined in patients. Moreover, the separation (PSS)-against-co-location (PSC) contrast revealed (1) activation of the SPL, precuneus and anterior cingulate cortex in controls, (2) suppression of the SPL and precuneus in patients, (3) activation of the pars triangularis of the inferior frontal gyrus and middle frontal gyrus in both controls and patients, (4) activation of the medial superior frontal gyrus in patients, and (5) impaired functional connectivity of the SPL in patients.

Introducing the PSS listening condition efficiently reveals both the brain substrates underlying schizophrenia-related speech-recognition deficits against informational masking and the schizophrenia-related neural compensatory strategy for impaired SPL functions.