Alzheimer Disease: Antal A

Kálmán J, Palotás A, Bódi N, Kincses TZ, Benedek G, Janka Z, Antal A. · Department of Psychiatry, Albert Szent-Györgyi Medical and Pharmaceutical Center, Faculty of Medicine, University of Szeged, H-6721 Szeged, Semmelweis u. 6, Hungary. · Brain Res Bull. · Pubmed #15862926 No free full text.

Abstract: Impaired neuronal energy metabolism, oxidative changes and microvascular abnormalities lead to altered lactate levels in Alzheimer's dementia. The aim of the present study was to assess whether intravenous sodium-lactate, a metabolic alternative and vasodilator that is thought to improve cognition, advances the cognitive performance of Alzheimer patients. Semantic categorization paradigm was used to present the electrophysiological correlates of natural scene categorization of Alzheimer patients before and after intravenous saline or sodium-lactate infusion. Mean amplitudes of event-related potentials (ERPs) were measured in two time windows before and after the treatments; two negative components (N1 between 150 and 250 ms and N2 between 400 and 600 ms) and one positive component (P2 between 250 and 400 ms) were identified. The negative components were more negative for the non-animal trials than for the animal trials while the positive component was similar for both categories. After the lactate treatment the amplitudes of the negative components became more negative mainly for the non-animal trials while the amplitude of the positive component turned more positive for the animal trials, however these changes were not significant. No changes have been observed after normal saline infusion. These results suggest that, contrary to its anticipated beneficial effects, sodium-lactate fails to significantly improve semantic categorization processes in Alzheimer's disease and this enhancement can be detected by recording ERPs. The effect of sodium-lactate to slightly improve semantic memory might be based on its positive effect on cardio- and cerebro-vascular function and neuronal metabolism.

Antal A, Kéri S, Kincses T, Kálmán J, Dibó G, Benedek G, Janka Z, Vécsei L. · Department of Physiology, University of Szeged, Szeged, Hungary. · Brain Res Cogn Brain Res. · Pubmed #11867250 No free full text.

Abstract: Previous studies have shown that briefly presented natural scenes containing non-animals elicited more negative potentials than images with animals even at 150 ms after stimulus onset (dN150). Cognitive models suggest that both feed-forward and feature weighting processes are involved in the rapid categorization of complex natural scenes. Here we examined the possible neuronal substrates of this model. Patients with Alzheimer's disease (AD) exhibited a delayed dN150, but in their case non-animals evoked more negative potentials similarly to the controls (presence of dN150). In contrast, in patients with Parkinson's disease (PD) animal and non-animal stimuli elicited nearly identical early responses (absence of dN150). The results indicate that when cortico-cortical pathways mediating feed-forward mechanisms are impaired (as in the case of AD), dN150 appears later, while in the case of corticostriatal dysfunctions (as in the case of PD) no differential response is present. This supports the hypothesis that corticostriatal circuits mediate perceptual feature weighting and integration in complex situations requiring categorical judgements.

Kéri S, Kálmán J, Rapcsak SZ, Antal A, Benedek G, Janka Z. · Department of Psychiatry, Albert Szent-Györgyi Medical University, Szeged, Hungary. · Brain. · Pubmed #10356059 links to  free full text

Abstract: Previous research has demonstrated that explicit recognition of dot patterns is impaired in amnesic patients with damage to the limbic-diencephalic memory system, while implicit categorization of the same kind of stimuli is preserved. The aim of the present study was to investigate the relationship between recognition and categorization performances in patients with Alzheimer's disease. Consistent with the findings in amnesic subjects, our results revealed that the explicit recognition of dot patterns was significantly impaired in Alzheimer's disease. However, implicit categorization functions were also disrupted. This was selective for the prototype stimuli; the categorization of non-prototype dot patterns was spared. The impaired category learning is likely to reflect the damage of modality-specific neocortical areas in Alzheimer's disease.

Kéri S, Antal A, Kálmán J, Janka Z, Benedek G. · Department of Psychiatry, Albert Szent-Györgyi Medical University, Szeged, Hungary. · Vision Res. · Pubmed #10343807 No free full text.

Abstract: Static and dynamic contrast sensitivity (SCS and DCS), semantic object identification, and verbal recall functions were evaluated in 20 Alzheimer's disease (AD) patients and in 20 control subjects. We found general SCS and DCS loss in the 0.48-14.34 c deg-1 spatial frequency range. In relation to the cognitive functions, semantic object identification was intact, whereas explicit memory was markedly impaired in the AD group. There was no significant correlation between the CS and the memory disturbances. The results suggest that early visual impairment and higher-level cognitive disturbances are independent in AD.