Ari Pääkkönen

Slowing of EEG in Parkinson's disease

EEG studies of Parkinsons disease (PD) have shown that the incidence of EEG abnormalities is higher than in normal old individuals. The most common alteration in PD is generalized slowing of the EEG. We studied 18 patients with Parkinson dementia, 18 age-matched Parkinson patients without dementia and 20 controls. The absolute and relative amplitudes of delta, theta, alpha and beta bands and the peak and mean frequency were calculated from EEG spectra recorded from the T6-O2 derivation. All variables differed significantly in Parkinson dementia patients compared to controls. The most conspicuous finding was the increase of delta activity. Parkinsonian patients without dementia had more theta activity and the frequencies were slow compared to controls. We conclude that parkinsonian subgroups have distinct patterns of abnormality in EEG spectra: Parkinson patients with dementia have distinctly slower EEGs than patients without dementia.

Serial EEG in Alzheimer's disease: 3 year follow-up and clinical outcome☆

We describe EEG findings and clinical outcomes of 24 Alzheimer (AD) patients over a 3 year follow-up period. Three records, baseline, 1 year and 3 year, were available for 13 patients. Although the majority of the patients showed slowing of the EEG over 3 years, evolutions of the EEG changes were not equal in all patients. In 12 (50%) of the patients the EEG from T6-O2 derivation was normal or slightly abnormal in the initial record and remained stable during 1 year. At year 3, only 2 patients still had normal EEGs and mild dementia, probably representing a subgroup of AD with a benign course, 7 patients needed institutional care and 3 had died. EEG slowing at the time of diagnosis was predictive of poor outcome at year 3; absolute theta amplitude was the best discriminating variable of outcome. The results support the idea of heterogeneity of AD patients and suggest that EEG may provide valuable information for prediction of outcome.

Gait characteristics and functional ambulation profile in patients with chronic unilateral stroke

Titianova EB, Pitkänen K, Pääkkönen A, Sivenius J, Tarkka IM: Gait characteristics and functional ambulation profile in patients with chronic unilateral stroke. Am J Phys Med Rehabil 2003;82:778–786. Objective Recent technical progress in gait analysis has resulted in portable walkways with embedded pressure-sensitive sensors. Often claims are made in connection with new equipment of their straightforward clinical use. The purpose of the present study was to assess whether the functional ambulation profile (FAP), calculated from walkway data, is a sensitive measure in the characterization of dissimilar patients with chronic hemiparesis due to stroke. Design We investigated the relationships between FAP and the type of stroke, patients’ functional disability, and spatial and temporal variables of gait obtained with the pressure sensor system walkway. Gait variables and FAP scores were compared in 25 patients with residual hemiparesis due to stroke and in 31 healthy subjects. Results A prolonged swing phase in the affected side and a prolonged stance phase in the nonaffected side were found in patients. Footprint pressure data revealed reduced peak pressure of the affected-side metatarsal area in patients, probably reflecting foot paresis. Higher Barthel Index score and lower Rankin Scale score were reflected in FAP scores. Conclusions The FAP scores of patients reflected well their characteristic spatio-temporal gait variations; however, the FAP score seemed a reliable measure of gait normality/abnormality only in rather unhurried gait. Thus, it is useful when a single number is needed.

Augmentation of Auditory N1 in Children with Fragile X Syndrome

We compared the N1 responses of the auditory event-related brain potentials (ERPs) in school-aged children with fragile X syndrome to age-matched controls in order to assess auditory processing. Event-related potentials to non-attended standard and deviant tone stimuli were recorded with EEG electrodes and here the standard tones were analysed. The amplitude of the N1 component to standard tones was significantly larger in children with fragile X syndrome than in control children. In addition, the global field power maximum of ERP corresponding to the N2 component was significantly (p<0.05) larger in fragile X children than in controls. The N2 scalp distribution in children with fragile X syndrome appeared more frontal than that in controls. Furthermore, the fragile X children exhibited no habituation of N1 and an absence of N2 sensitization for repeated tones. Increased responsiveness observed in the N1 evoked potential together with abnormal habituation of auditory responses in childhood may indicate increased sensory sensitivity for auditory stimuli in fragile X syndrome. The data, though very limited, suggest that stimulus processing in the auditory afferent pathways and/or in the corresponding cortical receiving areas is abnormal in children with fragile X syndrome.

Navigated TMS combined with EEG in mild cognitive impairment and Alzheimer's disease: a pilot study.

Our aim was to assess the potential of navigated transcranial magnetic stimulation (TMS)-evoked electroencephalographic (EEG) responses in studying neuronal reactivity and cortical connectivity in Alzheimers disease (AD) and in mild cognitive impairment (MCI). We studied 14 right-handed subjects: five patients with AD, five patients with MCI and four healthy controls. Fifty TMS-pulses at an intensity of 110% of individually determined motor threshold were delivered to the hand area of primary motor cortex (M1) with navigated brain stimulation (NBS). Spreading of primary NBS-evoked neuronal activity was monitored with a compatible 60-channel EEG, and analyzed in time, frequency and spatial-domains. We found significantly reduced TMS-evoked P30 (time-locked response 30 ms after the magnetic stimulation) in the AD subjects. This reduction was seen in the temporo-parietal area ipsilateral to stimulation side as well as in the contralateral fronto-central cortex corresponding to the sensorimotor network, which is anatomically interconnected with the stimulated M1. In addition, there was a significant decrease in the N100 amplitude in the MCI subjects when compared with the control subjects. Thus, the combination of NBS and EEG revealed prominent changes in functional cortical connectivity and reactivity in the AD subjects. This pilot study suggests that the method may provide a novel tool for examining the degree and progression of dementia.

Dual cerebral processing of elementary auditory input in children

WE compared event-related responses (ERPs) to nonattended frequent and intermittent auditory input in school-aged children and in young adults. In adults, both inputs elicited prominent auditory N100 responses at vertex. In children, intermittent stimulation evoked vertex responses with similar latency and refractoriness, whereas frequently delivered identical tones evoked responses on average at 240 ms. Sensitization of a separate neuronal population at 260–300 ms was obvious during intermittent stimulation in children. The dual behaviour, simultaneous ‘habituation’ of one neuronal population response and sensitization of another, may reflect the process of redirecting the attention and setting up a neuronal model. Furthermore, results suggest that a simplistic interpretation of developmental ERPs in which shortening of latencies represents maturation is insufficient.

Changes in absolute power values of EEG spectra in the follow‐up of Alzheimer's disease

We have studied the absolute and relative power and amplitude of EEG spectra (T6–02) of 24 patients with “probable” Alzheimers disease at the early stage of the disease and 1 year later and also compared the values to those of normal elderly controls. A remarkable variability of the absolute values was evident both for the patients and for the controls. The AD patients had significantly higher absolute theta amplitude and power and the absolute beta values tended to decrease compared to controls. Absolute delta and alpha values did not differ from those of the controls. The relative delta, theta and alpha power and amplitude, and beta amplitude showed significant changes in AD patients, whereas the relative beta power was unchanged. In the follow‐up of AD patients at 1 year, absolute alpha values decreased and delta values tended to increase. As to relative values, both the alpha and the delta significantly changed but the theta and the beta were unaltered. We conclude that both absolute and relative power and amplitude values should be considered in EEG studies of dementia patients. Absolute values are especially useful in follow‐up.

Visual Evoked Potentials, Brainstem Auditory Evoked Potentials, and Quantitative EEG in Baltic Progressive Myoclonus Epilepsy

Summary: Visual and brainstem auditory evoked potentials (VEP and BAEP, respectively) and quantitative EEG were studied in 16 patients with Baltic progressive myoclonus epilepsy (PME). The study demonstrated significantly delayed VEP latencies but normal amplitudes in Baltic PME. BAEPs showed slight but significant prolongation in central conduction time. Quantitative EEG revealed diminution of beta and alpha activity and accentuation of theta and delta activity. The slowing in VEP latencies is suggested to be due to impaired synaptic transmission and to reflect dopaminergic dysfunction in Baltic PME. We conclude that there is a multimodal disturbance in sensory projections to cortical areas in Baltic PME. The results give further evidence that nondemyelinating disorders—but with synaptic transmission defects—can produce changes in evoked potentials. The changes in epileptic brain are not confined to hyperexcitable epileptic neurons, but more widespread electrophysiological phenomena are produced.

Selective attention event-related potential effects from auditory novel stimuli in children and adults

OBJECTIVE We investigated differences between children and adults in selective attention. METHODS Event-related potentials of 9 year-old children and adults were studied. Subjects performed an active dichotic novelty oddball task. We examined age-related differences in early selection by comparing non-target tones and late selection by comparing target tones in the attended and unattended channels. RESULTS In children, an attention effect was seen on the N1 response to standard tones. For the targets, both children and adults displayed enhanced P3b amplitudes on the attended side, and in adults, an attention effect was also seen on the N2 response. In children, novelty-elicited N2 responses were larger to left ear stimuli irrespective of the direction of attention. Adults displayed enhanced novelty-elicited N2 amplitudes on the attended side. CONCLUSIONS Developmental changes occur both in early attentional selection and target detection. Children employed efficiently the mechanisms of early selection when processing standard stimuli, whereas their processes in relation to novel stimuli were attention-independent and even varied with ear. Adults were able to maintain their attentional focus in the presence of unexpected stimuli. SIGNIFICANCE The results of this study contribute to elucidation of the development of selective attention.

Effects of maternity on auditory event-related potentials to human sound.

Auditory event-related brain potentials (ERPs) were recorded in response to an emotional (a babys cry) and a neutral (a word) stimulus in a group of mothers 2–5 days after childbirth (n = 20) and in control women (n = 18) who were not in the state of early motherhood. For each mother, her own infants cry was recorded and used as the cry stimulus, whereas a strange babys cry was used for control women. The word stimulus was identical for both groups. Stimuli were presented in intermittent trains in order to study the arousal responses to the first stimuli of the trains, and refractoriness of ERPs during stimulus repetition. The N100 responses were significantly larger in amplitude in mothers than in control women, not only to the emotional cry stimuli but also to the neutral word stimuli. The finding suggests a general increase in alertness and arousal in mothers, which may be necessary in enabling the mother to be continuously alert to her infants needs. This allows good care of the infant and may be essential in building an emotional tie between the mother and her child.