Martin Grunwald

Hippocampal volume discriminates between normal cognition; questionable and mild dementia in the elderly

The sensitivity of MRI volumetric measures to detect cognitive dysfunction is examined in 39 participants of an epidemiological field study (age 75-85, MMSE 19-30). According to Clinical dementia rating (CDR), 17 subjects had normal cognition (CDR 0), 12 had questionable (CDR 0.5) and 10 mild dementia (CDR 1). Discriminant analysis based on four hippocampal measures resulted in a correct classification of 76.9% of all subjects. Left-sided and posterior hippocampal measures were more responsible for group discrimination than right-sided and anterior measures. In CDR 0.5, a significant hippocampal volume reduction of 14.3% vs.11.3% (left vs. right) relative to normal was found. The right hippocampus was significantly greater than the left in CDR 0 and CDR 0.5, but not in CDR 1. The magnitude of non-directional hippocampal asymmetry increased with decreasing cognitive state. We conclude that hippocampal atrophy is sensitive to detect cognitive dysfunction and subjects at risk for Alzheimers disease in the elderly population.

Human Haptic Perception: Basics and Applications

Haptic perception: an historical approach.-German pioneers of research into human haptic perception.-British pioneers of research into human haptic perception.-Early psychological studies on touch in France.-Haptics in the United States before 1940.-Anatomy of receptors.-Physiological mechanisms of the receptor system.-Neural basis of haptic perception.-The neural bases of haptic working memory.-Neuronal plasticity of the haptic system.-Haptic perception in the human fetus.-Haptic behavior in social interaction.-Learning effects in haptic perception.-Implicit and explicit memory effects in haptic perception.-Attention in sense of touch.-Haptic object identification.-Haptic perceptual illusions.-Haptic perception in interaction with other senses.-Haptically evoked activation of visual cortex.-Haptic perception and synaesthesia.-Haptic perception in sexuality.-Haptic perception in space travel.-Phantom sensations.-The neuroscience and phenomenology of sensory loss.-Focal dystonia: diagnostic, therapy, rehabilitation.-Self-injurious behavior.-Haptic perception in infancy and first acquisition of object words: developmental and clinical approach.-Haptic perception in anorexia nervosa.-History of haptic interfaces.-Principles of haptic perception in virtual environments.-Haptic shape cues, invariants, priors, and interface design.-Design guidelines for generating force feedback on fingertips using haptic interfaces.-Haptic rendering and control.-Haptic perception in human robotic systems.-Haptic design of vehicle interiors at AUDI.-Visual-haptic interfaces in car design at BMW.-Haptics research at Daimler AG.-Haptic design of handles.-Vestibular sensory substitution using tongue electrotactile display.-The blind get a taste of vision.-Tactile ground surface indicators in public places.-Haptic walker - haptic foot device for gait rehabilitation.-Haptic sensing of virtual textiles.-Haptic discrimination of paper.-Haptic banknote design.-Get touched - bodycare as adesign of media for self-perception.-

Correlation between cortical theta activity and hippocampal volumes in health, mild cognitive impairment, and mild dementia

Summary Cognitive decline is known to be associated with bothincreased &thgr; power over frontal regions and hippocampal atrophy. The aimof this study was to reveal the relation between these parameters in groupswith mild dementia, mild cognitive impairment, and healthy control subjects.The authors examined a preliminary randomly selected sample of 39 right-handedsubjects joining the Leipzig Longitudinal Study of the Aged, consisting of 17normal elderly subjects, 12 patients with mild cognitive impairment, and 10patients with mild dementia assessed by Clinical Dementia Rating. All subjectswere between 75 and 85 years old (mean age, 78 years; standard deviation, 2.78years) and underwent EEG and brain MRI. Mean spectral power densities werecalculated, and hippocampal body volume was measured. Significant negativelinear correlations between &thgr; power over frontal regions and hippocampalvolumes were found. The results support the assumption about a relationshipbetween hippocampal atrophy and &thgr; power, and may be helpful for a betterunderstanding of the course of Alzheimer’sdisease.

Power of theta waves in the EEG of human subjects increases during recall of haptic information

Several studies have reported a functional relationship between spectral power within the theta-band of the EEG (theta-power) and memory load while processing visual or semantic information. We investigated theta power during the processing of different complex haptic stimuli using a delayed recall design. The haptic explorations consisted of palpating the structure of twelve sunken reliefs with closed eyes. Subjects had to reproduce each relief by drawing it 10 s after the end of the exploration. The relationship between mean theta power and mean exploration time was analysed using a regression model. A linear relationship was found between the exploration time and theta power over fronto-central regions (Fp1, Fp2, F3, F7, F8, Fz, C3) directly before the recall of the relief. This result is interpreted in favour of the hypothesis that fronto-central theta power of the EEG correlates with the load of working memory independent of stimulus modality.

Theta power in the EEG of humans during ongoing processing in a haptic object recognition task

Dynamic changes in spectral theta power (TP) in the EEG over frontal regions were reported previously during the processing of visually presented spatial and verbal tasks [Cereb. Cortex, 7 (1997) 374-385]. Lower TP was found at the beginning compared to the end of processing. In order to test another modality, we examined theta power during the exploration of haptic stimuli with different complexity. A linear correlation between theta power and mean exploration time (as a measure of stimulus complexity) was found at the end of exploration but not at its beginning. These data are in line with our hypothesis since one could expect minimal load of working memory independent of stimulus complexity at the beginning of exploration whereas working memory would have integrated the stimuli of differing complexity into a perceptual model at the end of exploration.

Theta-power Differences in Patients with Mild Cognitive Impairment Under Rest Condition and During Haptic Tasks

The aim of this study was to investigate spectral EEG theta-power during perceptive-cognitive demands in age-homogenous groups of subjects with mild cognitive impairment (MCI), mild dementia (MDE), and a healthy control (CO) group. The present study includes 51 subjects (23 males, 28 females). We used the scales of the CDR (clinical dementia rating) to assign the subjects to the different groups. EEG data were collected during 10 minutes rest condition with eyes closed and during haptic perception test.The quality of the haptic reproductions differed significantly between CO and MCI, as well as between CO and MDE. The statistical comparison between EEG theta-power under rest condition and theta-power during haptic tasks revealed a significant decrease in theta-power during haptic tasks in all three groups over parieto-occipital regions. During haptic tasks, the theta-power was significantly different between CO and MDE over occipital regions and over parieto-temporal regions. A significant difference between CO and MCI was only revealed over right occipital regions (O2). Spectral theta-power during haptic tasks is a suitable measure to distinguish healthy subjects (CO) from patients with MCI respectively MDE. The results show that haptic tasks are sensitive to early perceptive-cognitive and functional deficits in patients with MCI.

Haptic Perception in Anorexia Nervosa Before and After Weight Gain

Haptic perception of patients with anorexia nervosa (n =10) was analyzed in a longitudinal study (T 0 T 1). The haptic explorations consisted of palpating the structure of 12 sunken reliefs in sequence with both hands, eyes closed. After each exploration the structure was reproduced on a piece of paper. In the anorexia group, mean exploration time was significantly shorter than in healthy control subjects. However, the reproductions of complex stimuli submitted by the anorexia group were of notably poorer quality than those of the healthy controls. This was also observed after weight gain (T 1). The results of the haptic explorations can be interpreted as a cortical dysfunction and deficits in somatosensorical integration processing in patients with anorexia nervosa. This may be due to a disorder of tactualspatial processing in the right parieto-occipital regions.

Age dependent changes of distractibility and reorienting of attention revisited: an event-related potential study

Adults of three age groups (18-27, 39-45, and 59-66 years) performed an auditory duration discrimination task with short (200 ms) or long (400 ms) sinusoidal tones. Performance was highly accurate and reaction times were on the same level in all groups, indicating no differences in auditory duration processing. Task irrelevant rare changes of the frequency of the stimuli were introduced to check whether the subjects, firstly, were distracted by changes in the environment while focusing on the task relevant information (indicated by prolonged responses), and, secondly, could re-focus on the relevant task after distraction. The results show that a distraction effect is present in all groups. Importantly, the 59-66 years group showed a behavioral distraction effect nearly twice as high as the other groups. The event-related brain potentials (ERPs) show mismatch negativity (MMN), P3a, and reorienting negativity (RON) elicited by deviants which are present in all groups. Aging effects on these ERP components were observable in all three components but a revealed a weak significant effect for the MMN only. Taken together, the behavioral and ERP results suggest that the function of balancing the processing of task irrelevant changes in the stimulation while focusing on task relevant information is effective during adulthood until the 7th decade of life.

Stable Asymmetric Interhemispheric Theta Power in Patients With Anorexia Nervosa During Haptic Perception Even After Weight Gain: A Longitudinal Study

The aim of this study was to investigate the interhemispheric brain electrical asymmetries during a resting period and during haptic tasks in theta frequency band (4–8 Hz) between healthy controls (N=10) and patients with anorexia nervosa (AN) (N=10). Additionally, AN patients were investigated twice in a longitudinal design (T0–T1) to analyze treatment effects. At rest, a theta asymmetry was observed in the AN group during an acute stage of starvation (T0) but not after weight gain (T1). Importantly, theta asymmetry over central regions (C3–C4) was observed in the AN group during the acute stage of starvation (T0) as well as after weight gain (T1) while performing haptic exploration tasks. In the control group, we found no significant theta asymmetry neither at rest nor during haptic explorations. Results are interpreted as an over-arousal of the right hemisphere in AN patients during complex multisensory integration processing which is possibly a result of general functional deficits of the right hemisphere.

Does the Hippocampal Atrophy Correlate With the Cortical Theta Power in Elderly Subjects With a Range of Cognitive Impairment

A previous study with a small sample (N = 39) showed a significant correlation between the cortical theta activity and the hippocampal volume in different stages of cognitive impairment in aged subjects. The recent study was aimed to replicate these results in a much bigger sample. The authors examined a sample of 121 right-handed subjects. The sample consisted of 37 healthy controls, 40 patients with questionable dementia, and 44 patients with mild dementia assessed by Clinical Dementia Rating. All subjects underwent EEG and brain MRI. Mean spectral power was calculated, and volume of hippocampal segments was measured. EEG theta power of the left and right hemisphere correlated significantly with the hippocampal volume on the left and right side in different stages of cognitive impairment. An increase of theta power was associated with decreased hippocampal volume. No other significant correlations were found for alpha or beta band power. No correlation was found between cortical theta and global brain volume. There seems to be a direct relationship between neuronal loss of the hippocampus and changed cortical theta activity for different stages of cognitive impairment in aged subjects.