[Ageing and working memory: the role of complexity and the type of information]. / Envejecimiento y memoria de trabajo: el papel de la complejidad y el tipo de informacion.

INTRODUCTION: Although there is agreement that working memory in older adults diminished with age, there is still controversy whether this reduction occurs equally for all kind of information or it is more pronounced for a particular type of information. AIM: To compare verbal working memory with visual and spatial working memory in young and older adults. These comparisons were examined at two levels of complexity. SUBJECTS AND METHODS: Two experiments were conducted, in one of them subjects performed the verbal and visual tasks, and in the other the verbal and spatial tasks. Forty-two subjects participated in each experiment: 21 young adults and 21 older adults. The n-back task (1-back and 2-back) was used with letters, abstract figures and circles at different positions to evaluate verbal, visual and spatial working memory, respectively. RESULTS: Older adults performed lower than young adults in the visual and spatial high difficult tasks. Working memory efficiency in the verbal task was equivalent in both groups, independently of the level of complexity; however, older adults' accuracy was lower in high complexity verbal task relative to the low complexity task. CONCLUSIONS: The findings suggest that working memory deficits during aging do not depend on the type of information but on the amount of resources from the memory system that each type of information requires to be processed.

[The neurophysiology of the interaction between attention and episodic memory: a review of studies into the visual mode]. / Neurofisiología de la interacción entre la atención y la memoria episódica: revisión de estudios en modalidad visual.

INTRODUCTION: Attention is the process that provides us with the capacity to select perceptions or internal representations for conscious processing and action. Given that episodic memory is where our personal experiences are stored together with the context they take place in, it has been observed that disturbances affecting attention, whether they are due to neurological disorders or experimental manipulation, deteriorate the storage of episodic information. AIMS: The aim of this study is to explain, from a neurophysiological perspective, how the processes of attention and memory interact with each other and which areas of the brain are involved in those processes. This objective is motivated by the fact that, despite empirical evidence supporting the interaction between the two processes, to our knowledge no reviews dealing with such an interaction have been published to date in the literature. DEVELOPMENT: In this work attention and memory are defined in terms of the neurophysiological changes that take place when the two processes occur. In what follows we offer a description of the systems that constitute attention, as well as those involved in the acquisition and recognition of information in episodic memory. Finally, we propose a possible explanation of how the mechanisms of interaction between these two processes work. CONCLUSIONS: The system of attention and the system of episodic memory are brought into play at the same time; the prefrontal cortex, in particular, plays a role in both processes. Attention seems to precede the mechanisms behind the acquisition of information while it is held during recognition.

Neurofisiología de la interacción entre la atención y la memoria episódica: revisión de estudios en modalidad visual / The neurophysiology of the interaction between attention and episodic memory: a review of studies into the visual mode

Introducción. La atención es el proceso mediante el cual somos capaces de seleccionar percepciones o representaciones internas para el procesamiento consciente y la acción. En tanto que la memoria episódica es el almacén de nuestras experiencias personales acompañadas del contexto en que ocurren, se ha observado que la perturbación de la atención, ya sea por un desorden neurológico o por la manipulación experimental, deteriora al almacén de información episódica. Objetivo. Explicar desde una perspectiva neurofisiológica cómo interactúan los procesos de atención y memoria, y cuáles son las regiones cerebrales que en ellos intervienen, ya que a pesar de la evidencia empírica sobre la interacción entre ambos procesos, no existe en la literatura, hasta donde es de nuestro conocimiento, una revisión que aborde tal interacción. Desarrollo. En la presente revisión se definen la atención y la memoria en función de los cambios neurofisiológicos que ocurren cuando se dan estos procesos. A continuación, se describen los sistemas que integran la atención y los que intervienen en la adquisición y el reconocimiento de la información en la memoria episódica. Finalmente, se propone una explicación de cómo ocurren, posiblemente, los mecanismos de interacción entre estos dos procesos. Conclusión. El sistema de atención participa de forma conjunta con el sistema de memoria episódica; particularmente, la corteza prefrontal tiene una función en ambos procesos. La atención parece preceder a los mecanismos de adquisición de la información mientras que se mantiene durante el reconocimiento

Introduction. Attention is the process that provides us with the capacity to select perceptions or internal representations for conscious processing and action. Given that episodic memory is where our personal experiences are stored together with the context they take place in, it has been observed that disturbances affecting attention, whether they are due to neurological disorders or experimental manipulation, deteriorate the storage of episodic information. Aims. The aim of this study is to explain, from a neurophysiological perspective, how the processes of attention and memory interact with each other and which areas of the brain are involved in those processes. This objective is motivated by the fact that, despite empirical evidence supporting the interaction between the two processes, to our knowledge no reviews dealing with such an interaction have been published to date in the literature. Development. In this work attention and memory are defined in terms of the neurophysiological changes that take place when the two processes occur. In what follows we offer a description of the systems that constitute attention, as well as those involved in the acquisition and recognition of information in episodic memory. Finally, we propose a possible explanation of how the mechanisms of interaction between these two processes work. Conclusions. The system of attention and the system of episodic memory are brought into play at the same time; the prefrontal cortex, in particular, plays a role in both processes. Attention seems to precede the mechanisms behind the acquisition of information while it is held during recognition

ERPs elicited by a cognitive incongruity paradigm: a semantic memory study.

The cognitive incongruity paradigm consists in presenting congruous or incongruous factual information to subjects, who are instructed to judge the truth of this information by comparing it with the factual knowledge stored in their semantic long-term memory. The factual information tested was whether a city presented after the name of a country, belongs (congruity) or not (incongruity) to that country. Results revealed that the recognition of incongruous factual information is characterized by a negative wave (N400), while the processing of congruous factual knowledge is characterized by a positive wave (P300) about 600 ms post-stimulus. In addition, these two components were sensitive to subject performance and subject confidence levels. The neurophysiological brain pattern observed during the cognitive incongruity paradigm reveals that the N400 and P300 are jointly affected by the task and reflect the recognition processes of factual knowledge.

What does the brain do while playing scrabble?: ERPs associated with a short-long-term memory task.

Event-related brain potentials (ERPs) were recorded while subjects performed the scrabble paradigm, a cued recall task that demands retrieving semantic memory information from long-term memory since subjects are not exposed to a previous study phase. The task combines short- and long-term memory processes and consists of forming words from a set of letters presented in random order. Short-term memory was manipulated by varying the number of letters (three, four and five) presented to the subject, while semantic memory was examined by comparing correct trials with no response trials. Behavioral results reveal that the subjects performed the task serially, as denoted by a linear reaction time increment as the number of random letters in the set increased. Short-term memory procedures were reflected by an amplitude increase of the N200 and by an amplitude decrease of the P300 increasing the number of letters. Successfully retrieving semantic information from long-term memory was indexed by a negative slow wave recorded at left frontal and left central sites, and by a positive slow wave predominant over right hemisphere sites. These findings provide evidence that semantic retrieval memory involves activity from both left and right hemispheres.

Neuromagnetic fields reveal cortical plasticity when learning an auditory discrimination task.

Auditory evoked neuromagnetic fields of the primary and association auditory cortices were recorded while subjects learned to discriminate small differences in frequency and intensity between two consecutive tones. When discrimination was no better than chance, evoked field patterns across the scalp manifested no significant differences between correct and incorrect responses. However, when performance was correct on at least 75% of the trials, the spatial pattern of magnetic field differed significantly between correct and incorrect responses during the first 70 ms following the onset of the second tone. In this respect, the magnetic field pattern predicted when the subject would make an incorrect judgment more than 100 ms prior to indicating the judgment by a button press. One subject improved discrimination for much smaller differences between stimuli after 200 h of training. Evidence of cortical plasticity with improved discrimination is provided by an accompanying decrease of the relative magnetic field amplitude of the 100 ms response components in the primary and association auditory cortices.

Aortic atherosclerosis and stroke.

METHODS: Studies using transesophageal echocardiography (TEE) suggest aortic atherosclerosis may be a risk factor for stroke, particularly stroke of undetermined mechanism, but controls in prior studies were not balanced for vascular risk factors. We used TEE to evaluate aortic atherosclerosis in 60 patients with stroke compared with a high-risk control population of 46 subjects. We also examined the possible association of plasma viscosity and fibrinogen levels to aortic atherosclerosis. RESULTS: The mean maximal plaque thickness (MMPT) was similar for the control (2.8 +/- 3.6 mm) and the stroke group (3.3 +/- 3.5 mm), but varied with stroke mechanism. The MMPT was similar in stroke of undetermined and atherosclerotic mechanism [3.5 +/- 4 mm (n = 25) and 4.2 +/- 4.3 mm (n = 16), respectively], significantly greater than in stroke of other mechanisms (1.7 +/- 1.2 mm, P < .05, n = 19). Patients with stroke of undetermined mechanism were four times more likely (95% confidence interval [CI] 1.2-12) to have plaques >/=5 mm compared with controls. Ulcerated plaque was associated with plaque thickness (P < .001) and plasma viscosity (P < .001). CONCLUSIONS: Aortic atherosclerosis is associated with stroke of undetermined cause suggesting atherosclerosis is a cause of stroke of undetermined etiology. Plaque ulceration was associated with the thickness of aortic plaque and plasma viscosity.

Prenatal and perinatal lead exposures alter acoustic cry parameters of neonate.

We performed acoustic analyses on cries elicited from a subset of healthy babies born to the Mexico City Prospective Lead Study at 2 days (n = 75), 15 days (n = 176), and 30 days (n = 166). Lead was measured in maternal blood every 8 weeks during pregnancy from week 12 to delivery and in umbilical cord (1-38 micrograms/dL, 0.05-1.84 mumol/L). Percent nasalization and number of cries decreased in babies born to mothers with higher lead levels in the last two trimesters while median fundamental frequency increased in babies born to mothers with higher lead at 12 weeks of pregnancy, and with higher cord lead in multiple regression analysis. Decreased percent nasalization was related to increased brainstem auditory evoked response latencies and interpeak intervals in a subset of the sample. The results suggest an effect of gestational exposure to lead on apparatus innervated by cranial nerves and/or lead effect on cry mediated by lead-altered auditory function. Altered baby cry and auditory function associated with lead might contribute to developmental delays by affecting early communication between caretaker and baby.

A comparative study of ERP correlates of psychometric and Piagetian intelligence measures in normal and hyperactive children.

Verbal and performance scores of the Wechsler Intelligence Scale for Children-Revised (WISC-R 1981) and of a Piagetian battery, the Cognitive Development Scale for Children (EDC 1984), were obtained on 30 normal control and 19 hyperactive 6-8-year-old children. Amplitudes and latencies of a fronto-central P250 and of the parieto-occipital N250, P350 and P500 were measured concurrently in 4 categorization tasks derived from tests of the WISC-R and EDC batteries. Spearman correlations were computed between the intelligence and the ERP factor scores. Results showed that age-related and age-corrected Wechsler's scores were correlated with similar ERP changes (reduced amplitude, decreased latency). With regard to the amplitude changes, each type of intelligence was associated with a specific ERP pattern. The verbal scores were correlated with the P350 and the P500 amplitudes, and the performance scores with the frontal P250 and occipital N250 amplitudes. By contrast, Piagetian development and intelligence scores yielded ERP correlates in the opposite direction: P500 amplitude was negatively correlated with raw EDC scores, but positively with scaled EDC scores. In addition, Piagetian intelligence was not related to the general peak latency decrease with age. In hyperactive children, additional negative correlations were found between P250 amplitude and the subjects' verbal test scores. Correlations with some performance tests that were negative in normal controls, were positive in hyperactive children. In addition, latency-based correlations found in normal controls were lacking in hyperactive children. These findings provide strong evidence that intelligence comprises different components related to different subsets of cognitive processes, as indexed by different ERP waves. They also suggest that the development and intelligence do not always rely on the same changes, and that intelligence forms may not be referred to the same use of the same processes in hyperactive and normal children.

Tonotopic organization of human auditory association cortex.

Neuromagnetic studies of responses in human auditory association cortex for tone burst stimuli provide evidence for a tonotopic organization. The magnetic source image for the 100 ms component evoked by the onset of a tone is qualitatively similar to that of primary cortex, with responses lying deeper beneath the scalp for progressively higher tone frequencies. However, the tonotopic sequence of association cortex in three subjects is found largely within the superior temporal sulcus, although in the right hemisphere of one subject some sources may be closer to the inferior temporal sulcus. The locus of responses for individual subjects suggests a progression across the cortical surface that is approximately proportional to the logarithm of the tone frequency, as observed previously for primary cortex, with the span of 10 mm for each decade in frequency being comparable for the two areas.