Search

According to the Cognitive reserve hypothesis, several factors related to mental engagement, such as level of education, type of occupation, leisure activities and social network, appear to affect the risk of developing clinical dementia. The present article provides an overview of the studies that have investigated the effects of mental engagement and cognitive stimulation specifically on dementia of the Alzheimer's type (AD). Mental training and cognitive stimulation interventions in AD have been shown to be useful in increasing patients' ability in performing activities of daily living (ADL), allowing them to maintain relative independence. Since cognitive engagement and stimulation are known to modify the brain processes to perform tasks, by recruiting alternative and more efficient networks, this review is especially focused on cognitive rehabilitation in AD patients, which has been shown to improve their global functioning and cognition. This perspective stresses the idea that cognitive reserve is not a fixed factor, but can be continuously modified by life experiences, even when the brain is already affected by neuropathology.

Working memory (WM), including a ‘central executive’, is used to guide behavior by internal goals or intentions. We suggest that WM is best described as a set of three interdependent functions which are implemented in the prefrontal cortex (PFC). These functions are maintenance, control of attention and integration. A model for the maintenance function is presented, and we will argue that this model can be extended to incorporate the other functions as well. Maintenance is the capacity to briefly maintain information in the absence of corresponding input, and even in the face of distracting information. We will argue that maintenance is based on recurrent loops between PFC and posterior parts of the brain, and probably within PFC as well. In these loops information can be held temporarily in an active form. We show that a model based on these structural ideas is capable of maintaining a limited number of neural patterns. Not the size, but the coherence of patterns (i.e., a chunking principle based on synchronous firing of interconnected cell assemblies) determines the maintenance capacity. A mechanism that optimizes coherent pattern segregation, also poses a limit to the number of assemblies (about four) that can concurrently reverberate. Top-down attentional control (in perception, action and memory retrieval) can be modelled by the modulation and re-entry of top-down information to posterior parts of the brain. Hierarchically organized modules in PFC create the possibility for information integration. We argue that large-scale multimodal integration of information creates an ‘episodic buffer’, and may even suffice for implementing a central executive.

Many recent behavioral and neuroscientific studies have revealed the importance of investigating meditation states and traits to achieve an increased understanding of cognitive and affective neuroplasticity, attention and self-awareness, as well as for their increasingly recognized clinical relevance. The investigation of states and traits related to meditation has especially pronounced implications for the neuroscience of attention, consciousness, self-awareness, empathy and theory of mind. In this article we present the main features of meditation-based mental training and characterize the current scientific approach to meditation states and traits with special reference to attention and consciousness, in light of the articles contributed to this issue.

Visual working memory is characterised by a limited storage capacity. Given this storage limitation, selection of behaviourally relevant objects based on locations, features or object category, is crucial. We conducted behavioural and ERP experiments to investigate location-based selection of multiple targets for storage in visual working memory, with a change detection paradigm. In the first experiment, the spatial locations of target-objects were marked in a preview display, before the appearance of target and distracter objects in the memory display. In the second experiment, spatial locations of distracter (response-irrelevant) objects were marked in the preview display. In the third experiment, a delay was introduced between preview and memory displays. In the forth experiment, the role of configuration-invariance in the transition between two subsequent preview displays, was investigated. The results show the effectiveness of the filtering is limited to two or three target objects, respectively. In addition, the filtering effect can be partly explained by selection of a global spatial configuration of location pre-cues, which is superimposed to the selection of individual object locations. In the fifth experiment, the neural processes of spatial marking of target locations were investigated by means of an ERP study. The results of this experiment show that filtering of target objects takes place both during encoding and maintenance of the memory display. The effect during maintenance was larger over the first half second of the maintenance interval. This time specificity suggests an attentional consolidation effect during the delayed activity of the neurons. Finally, we developed a neurocomputational model to account for the behavioural and ERP results.