Showing papers by "Rodrigo Quian Quiroga published in 2019"

Neural representations across species.

Abstract: Nonspatial cognitive factors modulate the firing of spatially tuned neurons A plethora of studies in rodents have described spatially tuned neurons, including place cells in the hippocampus and grid cells in the medial entorhinal cortex (MEC), suggesting a crucial role of the hippocampal formation in spatial navigation (1). Human studies have, in turn, shown that the hippocampal formation is involved in declarative memory (memories of facts and events) (2). What, then, is the function of the hippocampus? Is it involved in memory or in spatial navigation, or does it have a more general function that encompasses both? Several studies have shown that place cells remap, changing the location at which they respond, following geometrical changes in the environment, and that they can be modulated by nonspatial factors, according to the animals' specific tasks (3). These findings highlight the coding of cognitive components, challenging the notion that place cells represent an invariant spatial map. Although grid cells also realign with physical changes in the environment (4), the geometrical structure of their fields has been considered to provide a more invariant spatial representation. But do grid cells encode cognitive aspects as well? On pages 1443 and 1447 of this issue, Boccara et al. (5) and Butler et al. (6), respectively, show that this is the case, providing compelling evidence that grid cells are modulated by reward location. Complementing these studies, Baraduc et al. (7) showed that variations in spatially tuned neurons in the monkey hippocampus are accompanied by a “schema” of the task. Together these studies provide insights on how neurons in the hippocampal formation go beyond purely spatial representations and are modulated by cognitive factors.

A neural hallmark of auditory implicit learning is altered in older adults.

Abstract: Temporal regularities in the environment are often learned implicitly. In an auditory target-detection paradigm using EEG, Jongsma and colleagues (2006) showed that the neural response to these implicit regularities results in a reduction of the P3-N2 complex. Here, we utilized the same paradigm, this time in both young and old participants, to determine if this EEG signature of implicit learning was altered with age. Behaviorally, both groups of participants showed similar benefits for the presence of temporal regularity, with faster and more accurate responses given when the auditory targets were presented in a temporally regular vs. random pattern. In the brain, the younger adults showed the expected decrease in amplitude of this complex for regular compared to irregular trials. Older adults, in contrast, showed no difference in the amplitude of the P3-N2 complex between the irregular and regular condition. These data suggest that, although auditory implicit learning may be behaviorally spared in aging, older adults are not using the same neural substrates as younger adults to achieve this.