RESUMO
BACKGROUND: Patients with borderline personality disorder (BPD) show negative and unstable self- and other-evaluations compared to healthy individuals. It is unclear, however, how they process self- and other-relevant social feedback. We have previously demonstrated a positive updating bias in healthy individuals: When receiving social feedback on character traits, healthy individuals integrate desirable more than undesirable feedback. Here, our aim was to test whether BPD patients exhibit a more negative pattern of social feedback processing. METHOD: We employed a character trait task in which BPD patients interacted with four healthy participants in a real-life social interaction. Afterwards, all participants rated themselves and one other participant on 80 character traits before and after receiving feedback from their interaction partners. We compared how participants updated their ratings after receiving desirable and undesirable feedback. Our analyses included 22 BPD patients and 81 healthy controls. RESULTS: Healthy controls showed a positivity bias for self- and other-relevant feedback as previously demonstrated. Importantly, this pattern was altered in BPD patients: They integrated undesirable feedback for themselves to a greater degree than healthy controls did. Other-relevant feedback processing was unaltered in BPD patients. CONCLUSIONS: Our study demonstrates an alteration in self-relevant feedback processing in BPD patients that might contribute to unstable and negative self-evaluations.
Assuntos
Transtorno da Personalidade Borderline/psicologia , Retroalimentação Psicológica , Relações Interpessoais , Adolescente , Adulto , Estudos de Casos e Controles , Feminino , Alemanha , Humanos , Autoavaliação (Psicologia) , Adulto JovemRESUMO
Recent studies reported reductions of well-established biases in decision making under risk, such as the framing effect, during foreign language (FL) use. These modulations were attributed to the use of FL itself, which putatively entails an increase in emotional distance. A reduced framing effect in this setting, however, might also result from enhanced cognitive control associated with language-switching in mixed-language contexts, an account that has not been tested yet. Here we assess predictions of the 2 accounts in 2 experiments with over 1,500 participants. In Experiment 1, we tested a central prediction of the emotional distance account, namely that the framing effect would be reduced at low, but not high, FL proficiency levels. We found a strong framing effect in the native language, and surprisingly also in the foreign language, independent of proficiency. In Experiment 2, we orthogonally manipulated foreign language use and language switching to concurrently test the validity of both accounts. As in Experiment 1, foreign language use per se had no effect on framing. Crucially, the framing effect was reduced following a language switch, both when switching into the foreign and the native language. Thus, our results suggest that reduced framing effects are not mediated by increased emotional distance in a foreign language, but by transient enhancement of cognitive control, putting the interplay of bilingualism and decision making in a new light. (PsycINFO Database Record
Assuntos
Tomada de Decisões , Emoções , Função Executiva , Multilinguismo , Adulto , Feminino , Humanos , Testes de Linguagem , Masculino , Competência Profissional , Testes Psicológicos , Tempo de Reação , Autorrelato , Adulto JovemRESUMO
BACKGROUND: When challenged with information about the future, healthy participants show an optimistically biased updating pattern, taking desirable information more into account than undesirable information. However, it is unknown how patients suffering from major depressive disorder (MDD), who express pervasive pessimistic beliefs, update their beliefs when receiving information about their future. Here we tested whether an optimistically biased information processing pattern found in healthy individuals is absent in MDD patients. METHOD: MDD patients (n = 18; 13 medicated; eight with co-morbid anxiety disorder) and healthy controls (n = 19) estimated their personal probability of experiencing 70 adverse life events. After each estimate participants were presented with the average probability of the event occurring to a person living in the same sociocultural environment. This information could be desirable (i.e. average probability better than expected) or undesirable (i.e. average probability worse than expected). To assess how desirable versus undesirable information influenced beliefs, participants estimated their personal probability of experiencing the 70 events a second time. RESULTS: Healthy controls showed an optimistic bias in updating, that is they changed their beliefs more toward desirable versus undesirable information. Overall, this optimistic bias was absent in MDD patients. Symptom severity correlated with biased updating: more severely depressed individuals showed a more pessimistic updating pattern. Furthermore, MDD patients estimated the probability of experiencing adverse life events as higher than healthy controls. CONCLUSIONS: Our findings raise the intriguing possibility that optimistically biased updating of expectations about one's personal future is associated with mental health.
Assuntos
Antecipação Psicológica/fisiologia , Transtorno Depressivo Maior/psicologia , Esperança , Acontecimentos que Mudam a Vida , Enquadramento Psicológico , Adulto , Análise de Variância , Transtornos de Ansiedade/complicações , Transtornos de Ansiedade/psicologia , Estudos de Casos e Controles , Transtorno Depressivo Maior/complicações , Feminino , Humanos , Imaginação , Testes de Inteligência , Entrevista Psicológica , Masculino , Modelos Psicológicos , Probabilidade , Escalas de Graduação Psiquiátrica , Índice de Gravidade de DoençaRESUMO
We investigated how the microstructure of relevant white matter connections is associated with cortical responsivity and working memory (WM) performance by collecting diffusion tensor imaging and verbal WM functional magnetic resonance imaging data from 29 young adults. We measured cortical responsivity within the frontoparietal WM network as the difference in blood oxygenation level-dependent (BOLD) signal between 3-back and 1-back conditions. Fractional anisotropy served as an index of the integrity of the superior longitudinal fasciculi (SLF), which connect frontal and posterior regions. We found that SLF integrity is associated with better 3-back performance and greater task-related BOLD responsivity. In addition, BOLD responsivity in right premotor cortex reliably mediated the effects of SLF integrity on 3-back performance but did not uniquely predict 3-back performance after controlling for individual differences in SLF integrity. Our results suggest that task-related adjustments of local gray matter processing are conditioned by the properties of anatomical connections between relevant cortical regions. We suggest that the microarchitecture of white matter tracts influences the speed of signal transduction along axons. This in turn may affect signal summation at neural dendrites, action potential firing, and the resulting BOLD signal change and responsivity.
Assuntos
Lobo Frontal/fisiologia , Memória de Curto Prazo/fisiologia , Rede Nervosa/fisiologia , Lobo Parietal/fisiologia , Desempenho Psicomotor/fisiologia , Adulto , Mapeamento Encefálico/métodos , Feminino , Humanos , Masculino , Valor Preditivo dos Testes , Adulto JovemRESUMO
We collected MRI diffusion tensor imaging data from 80 younger (20-32 years) and 63 older (60-71 years) healthy adults. Tract-based spatial statistics (TBSS) analysis revealed that white matter integrity, as indicated by decreased fractional anisotropy (FA), was disrupted in numerous structures in older compared to younger adults. These regions displayed five distinct region-specific patterns of age-related differences in other diffusivity properties: (1) increases in both radial and mean diffusivity; (2) increases in radial diffusivity; (3) no differences in parameters other than FA; (4) a decrease in axial and an increase in radial diffusivity; and (5) a decrease in axial and mean diffusivity. These patterns suggest different biological underpinnings of age-related decline in FA, such as demyelination, Wallerian degeneration, gliosis, and severe fiber loss, and may represent stages in a cascade of age-related degeneration in white matter microstructure. This first simultaneous description of age-related differences in FA, mean, axial, and radial diffusivity requires histological and functional validation as well as analyses of intermediate age groups and longitudinal samples.
Assuntos
Envelhecimento/patologia , Encéfalo/anatomia & histologia , Adulto , Idoso , Imagem de Tensor de Difusão , Feminino , Humanos , Interpretação de Imagem Assistida por Computador , Masculino , Pessoa de Meia-Idade , Adulto JovemRESUMO
Perceptual decision making typically entails the processing of sensory signals, the formation of a decision, and the planning and execution of a motor response. Although recent studies in monkeys and humans have revealed possible neural mechanisms for perceptual decision making, much less is known about how the decision is subsequently transformed into a motor action and whether or not the decision is represented at an abstract level, i.e., independently of the specific motor response. To address this issue, we used functional MRI to monitor changes in brain activity while human subjects discriminated the direction of motion in random-dot visual stimuli that varied in coherence and responded with either button presses or saccadic eye movements. We hypothesized that areas representing decision variables should respond more to high- than to low-coherence stimuli independent of the motor system used to express a decision. Four areas were found that fulfilled this condition: left posterior dorsolateral prefrontal cortex (DLPFC), left posterior cingulate cortex, left inferior parietal lobule, and left fusifom/parahippocampal gyrus. We previously found that, when subjects made categorical decisions about degraded face and house stimuli, left posterior DLPFC showed a greater response to high- relative to low-coherence stimuli. Furthermore, the left posterior DLPFC appears to perform a comparison of signals from sensory processing areas during perceptual decision making. These data suggest that the involvement of left posterior DLPFC in perceptual decision making transcends both task and response specificity, thereby enabling a flexible link among sensory evidence, decision, and action.
Assuntos
Mapeamento Encefálico , Tomada de Decisões/fisiologia , Percepção/fisiologia , Córtex Pré-Frontal/fisiologia , Adulto , Comportamento/fisiologia , Feminino , Humanos , Imageamento por Ressonância Magnética , MasculinoRESUMO
Healthy aging is associated with a number of neuroanatomical and neurobiological alterations that result in various cognitive changes. Both, the dopaminergic as well as the serotonergic system are subject to change during aging. Receptor loss and severe structural changes in PFC and striatum have been reported. Aging is associated with a progressive decline in several cognitive functions, such as episodic memory, working memory, and processing speed. Furthermore, it is associated with deficits in tasks requiring adaptation to external feedback of right or wrong, or task-switching. Here, we develop the hypothesis that this loss of behavioral flexibility is caused by structural and functional alterations of the reward system leading to impairments in reward processing, learning stimulus reinforcement associations, and reward-based decision-making. We review (a) data on neural correlates and substrates of reward processing in young healthy animals and humans, (b) evidence for age related functional and structural alterations of the reward system, and (c) behavioral and neuroimaging data of age effects on reward-based decision-making processes. Implications for neuroeconomics and neurodegenerative diseases are discussed.
Assuntos
Envelhecimento/fisiologia , Transtornos Cognitivos/fisiopatologia , Tomada de Decisões/fisiologia , Transtornos da Memória/fisiopatologia , Recompensa , Envelhecimento/patologia , Animais , Encéfalo/patologia , Encéfalo/fisiologia , Encéfalo/fisiopatologia , Transtornos Cognitivos/etiologia , Transtornos Cognitivos/patologia , Modelos Animais de Doenças , Humanos , Deficiências da Aprendizagem/etiologia , Deficiências da Aprendizagem/patologia , Deficiências da Aprendizagem/fisiopatologia , Transtornos da Memória/patologia , Vias Neurais/patologia , Vias Neurais/fisiologia , Vias Neurais/fisiopatologiaRESUMO
The flexible learning of stimulus-reward associations when required by situational context is essential for everyday behavior. Older adults experience a progressive decline in several cognitive functions and show deficiencies in neuropsychological tasks requiring flexible adaptation to external feedback, which could be related to impairments in reward association learning. To study the effect of aging on stimulus-reward association learning 20 young and 20 older adults performed a probabilistic object reversal task (pORT) along with a battery of tests assessing executive functions and general intellectual abilities. The pORT requires learning and reversing associations between actions and their outcomes. Older participants collected fewer points, needed more trials to reach the learning criterion, and completed less blocks successfully compared to young adults. This difference remained statistically significant after correcting for the age effect of other tests assessing executive functions. This suggests that there is an age-related difference in reward association learning as measured using the pORT, which is not closely related to other executive functions with respect to the age effect. In human aging, structural alterations of reward detecting structures and functional changes of the dopaminergic as well as the serotonergic system might contribute to the deficit in reward association learning observed in this study.
Assuntos
Envelhecimento/psicologia , Aprendizagem por Associação , Reforço Psicológico , Adulto , Idoso , Tomada de Decisões , Feminino , Objetivos , Humanos , Masculino , Análise e Desempenho de TarefasRESUMO
Findings from single-cell recording studies suggest that a comparison of the outputs of different pools of selectively tuned lower-level sensory neurons may be a general mechanism by which higher-level brain regions compute perceptual decisions. For example, when monkeys must decide whether a noisy field of dots is moving upward or downward, a decision can be formed by computing the difference in responses between lower-level neurons sensitive to upward motion and those sensitive to downward motion. Here we use functional magnetic resonance imaging and a categorization task in which subjects decide whether an image presented is a face or a house to test whether a similar mechanism is also at work for more complex decisions in the human brain and, if so, where in the brain this computation might be performed. Activity within the left dorsolateral prefrontal cortex is greater during easy decisions than during difficult decisions, covaries with the difference signal between face- and house-selective regions in the ventral temporal cortex, and predicts behavioural performance in the categorization task. These findings show that even for complex object categories, the comparison of the outputs of different pools of selectively tuned neurons could be a general mechanism by which the human brain computes perceptual decisions.
Assuntos
Encéfalo/fisiologia , Tomada de Decisões/fisiologia , Modelos Neurológicos , Percepção Visual/fisiologia , Animais , Atenção/fisiologia , Encéfalo/citologia , Face , Feminino , Haplorrinos/fisiologia , Habitação , Humanos , Imageamento por Ressonância Magnética , Masculino , Reconhecimento Visual de Modelos/fisiologia , Estimulação Luminosa , Córtex Pré-Frontal/citologia , Córtex Pré-Frontal/fisiologiaRESUMO
This study investigated how a decrease in neuronal activity affects cerebral blood oxygenation employing a paradigm of acoustically triggered saccades in complete darkness. Known from behavioral evidence as saccadic suppression, electrophysiologically it has been shown in monkeys that during saccades an attenuation of activity occurs in visual cortex neurons (Duffy and Burchfiel, 1975). In study A, using blood oxygen level-dependent (BOLD) contrast functional magnetic resonance imaging (fMRI), the authors observed signal intensity decreases bilaterally at the occipital pole during the performance of saccades at 2 Hz. In study B.1, the authors directly measured changes in deoxyhemoglobin [deoxy-Hb] and oxyhemoglobin [oxy-Hb] concentration in the occipital cortex with near-infrared spectroscopy (NIRS). Whereas a rise in [deoxy-Hb] during the performance of saccades occurred, there was a drop in [oxy-Hb]. In a second NIRS study (B.2), subjects performed saccades at different rates (1.6, 2.0, and 2.3 Hz). Here the authors found the increase in deoxy-Hb and the decrease of oxy-Hb to be dependent on the frequency of the saccades. In summary, the authors observed a focal hypooxygenation in the human visual cortex dependent on the saccade-frequency in an acoustically triggered saccades paradigm. This could be interpreted as evidence that corresponding to the focal hyperoxygenation observed in functional brain activation, caused by an excessive increase in cerebral blood flow (CBF) over the increase in CMRO2 during decreased neuronal activity CBF, is more reduced than oxygen delivery.
Assuntos
Lobo Occipital/metabolismo , Consumo de Oxigênio/fisiologia , Movimentos Sacádicos/fisiologia , Estimulação Acústica , Adulto , Circulação Cerebrovascular , Sinais (Psicologia) , Feminino , Hemoglobinas/análise , Humanos , Imageamento por Ressonância Magnética , Masculino , Oxigênio/sangue , Oxiemoglobinas/análise , Estimulação Luminosa , Espectroscopia de Luz Próxima ao InfravermelhoRESUMO
In this study the authors used a whole-spectrum near-infrared spectroscopy approach to noninvasively assess changes in hemoglobin oxygenation and cytochrome-c oxidase redox state (Cyt-Ox) in the occipital cortex during visual stimulation. The system uses a white light source (halogen lamp). The light reflected from the subject's head is spectrally resolved by a spectrograph and dispersed on a cooled charge-coupled device camera. The authors showed the following using this approach: (1) Changes in cerebral hemoglobin oxygenation (increase in concentration of oxygenated hemoglobin, decrease in concentration of deoxygenated hemoglobin) in the human occipital cortex during visual stimulation can be assessed quantitatively. (2) The spectral changes during functional activation cannot be completely explained by changes in hemoglobin oxygenation solely; Cyt-Ox has to be included in the analysis. Only if Cyt-Ox is considered can the spectral changes in response to increased brain activity be explained. (3) Cytochrome-c oxidase in the occipital cortex of human subjects is transiently oxidized during visual stimulation. This allows us to measure vascular and intracellular energy status simultaneously.
Assuntos
Córtex Cerebral/enzimologia , Complexo IV da Cadeia de Transporte de Elétrons/metabolismo , Estimulação Luminosa , Adulto , Feminino , Hemoglobinometria , Humanos , Masculino , Oxirredução , Consumo de Oxigênio/fisiologia , Espectroscopia de Luz Próxima ao InfravermelhoRESUMO
For the calculation of changes in oxyhaemoglobin, deoxyhaemoglobin and the redox state of cytochrome-c-oxidase from attenuation data via a modified Beer-Lambert equation the wavelength dependence of the differential pathlength factor (DPF(lambda)) has to be taken into account. The DPF, i.e. the ratio of the mean optical pathlength and the physical light source-detector separation at each wavelength, determines the crosstalk between the different concentrations and is therefore essential for a sensitive detection of chromophore changes. Here a simple method is suggested to estimate the wavelength dependence of the DPF(lambda) from pulse-induced attenuation changes measured on the head of adult humans. The essence is that the DPF is the ratio of the attenuation changes over absorption coefficient changes, and that the spectral form of the pulse correlated absorption coefficient change can be assumed to be proportional to the extinction coefficient of blood. Indicators for the validity of the DPF(lambda) derived for wavelengths between 700 and 970 nm are the stability of the calculated haemoglobin and cytochrome signals with variations of the wavelength range included for their calculation and its overall agreement with the data available from the literature.
Assuntos
Encéfalo/metabolismo , Espectroscopia de Luz Próxima ao Infravermelho/métodos , Adulto , Fenômenos Biofísicos , Biofísica , Circulação Cerebrovascular , Complexo IV da Cadeia de Transporte de Elétrons/química , Complexo IV da Cadeia de Transporte de Elétrons/metabolismo , Hemoglobinas/análise , Hemoglobinas/metabolismo , Humanos , Oxirredução , Oxigênio/sangue , Oxiemoglobinas/análise , Oxiemoglobinas/metabolismo , Reprodutibilidade dos Testes , Espectroscopia de Luz Próxima ao Infravermelho/estatística & dados numéricosRESUMO
Using near-infrared spectroscopy, we investigated the time-course of the concentrations of oxygenated haemoglobin, [oxy-Hb], and deoxygenated haemoglobin [deoxy-Hb], in the occipital cortex of healthy human adults during standard sustained visual stimulation. Within a few seconds after stimulation (by coloured dodecahedron), we observed a decrease in [deoxy-Hb], peaking after 13 s ('initial undershoot'). In the subsequent 1-2 min, in seven out of ten subjects, [deoxy-Hb] gradually returned to a plateau closer to the baseline level. After cessation of stimulation, there was a 'post-stimulus overshoot' in [deoxy-Hb]. There was a statistically significant correlation between the size of the 'initial undershoot' and the post-stimulus overshoot'. The concentration of oxyhaemoglobin increased upon functional activation. However, in the mean across all subjects there was no 'initial overshoot'. After approximately 19 s it reached a plateau and remained constantly elevated throughout the activation period. After cessation of activation there was a 'post-stimulus undershoot' of oxyhaemoglobin. It is important to consider the time-course of haemoglobin oxygenation when interpreting functional activation data, especially those data obtained with oxygenation-sensitive methods, such as BOLD-contrast fMRI.
Assuntos
Percepção de Cores , Hemoglobinas/metabolismo , Lobo Occipital/irrigação sanguínea , Lobo Occipital/metabolismo , Oxiemoglobinas/metabolismo , Estimulação Luminosa , Adulto , Feminino , Humanos , Cinética , Masculino , Análise de Regressão , Espectrofotometria Infravermelho/métodosRESUMO
We used near-infrared spectroscopy (NIRS) to study non-invasively changes in cerebral hemoglobin oxygenation in the frontal and parietal cortex during performance of a verbal fluency task in patients with Alzheimer's disease (AD). Whereas healthy elderly subjects (n = 19, age 67 +/- 10 years) showed increases in concentrations of oxygenated hemoglobin [HbO2] (mean (arbitrary units) +/- S.E.M., 1.44 +/- 0.59) and total hemoglobin [HbT] (0.92 +/- 0.81) over the left superior parietal cortex, patients with AD (n = 19, age 71 +/- 10 years) showed significant decreases in [HbO2] (-3.26 +/- 1.30, P < 0.01) as well as [HbT] (-4.45 +/- 1.57, P < 0.01). [HbR] decreased slightly in both groups (-0.62 +/- 0.29 and - 1.18 +/- 0.40, respectively). Using two pairs of NIRS optodes placed on the left superior partietal cortex and on the left prefrontal cortex simultaneous increases in [HbO2] as well as [HbT] in both cortical regions in the healthy elderly subjects (n = 8, age 60 +/- 15) were demonstrated during performance of the task. AD patients (n = 10, age 65 +/- 13 years) showed decreases in [HbO2] and [HbT] in the parietal cortex and, at the same time, increases in [HbO2] and [HbT] in the frontal cortex. Simultaneous NIRS-[HbT] and PET-rCBF measurements showed a significant correlation both when calculated in a 'banana' shaped volume approximated by using cortical thresholds as well as when calculated in a semisphere volume of brain tissue beneath the optodes placed on the head surface (patients with AD, n = 10). The correlation was dependent on the assumed penetration depth of the near-infrared light and was best for all three NIRS variables ([HbO2], [HbR] and [HbT]) when calculated using a semisphere radius of 0.45 cm to 1.35 cm. In conclusion, in Alzheimer's disease a marked reduction of regional cerebral blood flow and cerebral hemoglobin oxygenation may occur during activation of brain function, probably mainly in degenerating brain areas, such as the parietal cortex.
Assuntos
Circulação Cerebrovascular/fisiologia , Hemoglobinas/metabolismo , Oxigênio/sangue , Lobo Parietal/metabolismo , Comportamento Verbal/fisiologia , Idoso , Estudos de Casos e Controles , Feminino , Humanos , Modelos Lineares , Masculino , Pessoa de Meia-Idade , Reprodutibilidade dos Testes , Espectrofotometria Infravermelho , Tomografia Computadorizada de EmissãoAssuntos
Hemoglobinas/metabolismo , Lobo Occipital/fisiologia , Oxiemoglobinas/metabolismo , Visão Ocular/fisiologia , Córtex Visual/fisiologia , Adulto , Percepção de Cores , Feminino , Humanos , Masculino , Percepção de Movimento , Desempenho Psicomotor , Tempo de Reação , Espectrofotometria Infravermelho/métodosRESUMO
In a retrospective analysis of 752 consecutive medical reports of patients with insulin- or non-insulin-dependent diabetes mellitus, we investigated the completeness of documentation of indicators of quality of care. The medical reports are the currently used form of documentation which is sent to the General Practitioner after the patient's discharge from hospital. The indicators of care were data on clinical history, physical examination, laboratory results and secondary complications. The documentation was incomplete; e.g. in 8.0% of insulin-dependent (IDDM) and in 26.4% of non-insulin-dependent diabetics (NIDDM), HbA1c was missing. In 7.6%, the type of diabetes was not stated. The frequency of recorded secondary complications was lower than it has to be expected considering metabolic control and duration of diabetes of the studied group. Documentation was more complete for IDDM patients. The reports of NIDDM patients with incipient or overt diabetic nephropathy revealed less frequent recordings of data on lipid metabolism and blood pressure compared to the group without nephropathy. The documentation of indicators of quality of care in medical reports for general practitioners is incomplete for many diabetic inpatients. Standardized methods of documentation are required urgently.
Assuntos
Diabetes Mellitus/terapia , Auditoria Médica , Prontuários Médicos/normas , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Criança , Continuidade da Assistência ao Paciente/normas , Complicações do Diabetes , Diabetes Mellitus/diagnóstico , Documentação/normas , Medicina de Família e Comunidade , Alemanha , Humanos , Pessoa de Meia-Idade , Alta do Paciente , Estudos RetrospectivosRESUMO
Near infrared spectroscopy (NIRS) is a new technique that permits noninvasive monitoring of cerebral blood and tissue oxygenation. Recently, we and others have shown that NIRS measurements are sensitive enough to follow changes in cerebral hemoglobin oxygenation due to activation of brain function. Based on these findings we have assessed the influence of aging as well as the influence of neurodegeneration on cerebral hemoglobin oxygenation during mental work. The typical NIRS pattern in young healthy subjects while performing calculation tasks measured in the frontal cortex were increases in oxygenated hemoglobin [HbO2] and total hemoglobin [HbT] while reduced hemoglobin [HbR] decreased. Elderly healthy subjects showed a significant lower mean increase in [HbO2] and [HbT] levels. Regression analysis revealed an age-dependent decline in activation-induced local increase of [HbO2] as well as [HbT]. Furthermore, we monitored changes in cerebral hemoglobin oxygenation in the frontal cortex while patients with probable Alzheimer's disease (AD) performed cognitive tasks. Whereas elderly healthy subjects (as well as patients with major depression, age-associated memory impairments or vascular dementia) again showed clear increases in the local concentrations of [HbO2] and [HbT] during brain activation, AD patients showed significant decreases compared to the baseline levels in both variables that were most pronounced in the parietal cortex. To clarify whether the different patterns in cerebral hemoglobin oxygenation during cognitive activation were due to an altered functional brain organization in AD or to alterations in the cerebrovascular response to neuronal activation, we are currently performing simultaneous NIRS and (015-H20-)PET measurements during performance of a cognitive task (Stroop test). Our finding of a regional reduced oxygen supply during activation of brain function may be of relevance to the development and the time course of neurodegeneration.