#Neuros mpeg recorder 2 series

After each run of Task 2, the learning of associations was tested in Task 3 (the patient was presented each face at a time and had to select the landmark corresponding to it). The instructions were the same as in Task 1 (i.e., indicate presence of a human face). In Task 2, the composite images (each of them being a specific person in a specific place) were presented in pseudorandom order, which were then followed by the presentation of the single pictures, also in pseudorandom order. Then, a block of “learning and evaluation trials” (median of 15 trials) comprising interleaved tasks 2 and 3 were shown. First, to get an estimation of the pre-learning firing to each picture, in Task 1, the screening was repeated showing each of the single pictures for 1 s 6 times in pseudorandom order, and patients were asked to indicate whether the picture contained a human face or not.

Using presentations of the single and composite images of each pair, we evaluated changes in neural activity while subjects performed five consecutive tasks ( Figure 1). For each pair, we created contextual “composite” images, in which each individual was digitally extracted from the original picture and placed in front of the landmark, mimicking a real photo of seeing the individual at that landmark ( Figure 1). Each pair consisted of a picture of a person (or animal) and a picture of a landmark, for which there was a neuron firing to one of them (the preferred “P” stimulus) and not to the other one (the non-preferred “NP” stimulus). Data processing (spike detection, sorting, and identification of responsive cells) was done quickly (typically within 1 hr) and 3 to 8 (median 7) pairs of pictures were selected. Patients first participated in a “screening session” ( Quian Quiroga et al., 2005) in which a large number of images of people, animals, and places were presented to find out which (if any) of the recorded neurons responded to a picture. As detailed below, in order to gain such evidence, we combined the ability to analyze trial-by-trial changes in the robust firing of highly selective MTL neurons ( Quian Quiroga et al., 2005, 2008, 2009), with the rapid facility that humans have for learning complex associations and consciously declare them. We postulate that associations can be formed by partially overlapping cell assemblies encoding related concepts ( Quian Quiroga, 2012) and show experimental evidence of rapid changes of single-cell responses while contextual associations are learned. Here we designed a paradigm to study how fast these associations can be created and whether this speed is compatible with basic mechanisms of episodic memory creation.

#Neuros mpeg recorder 2 series

Neurons in the human MTL have been found to respond to concepts that are related to each other ( Quian Quiroga, 2012 Quian Quiroga et al., 2005), such as two co-stars in the same television series or a few researchers (previously unknown to the patients) involved in the experiments ( Quian Quiroga et al., 2009 Viskontas et al., 2009). Animal studies, on the other hand, have relied on extensive reward-driven training with numerous repetitions of non-natural stimuli, thus offering a limited account on how single exposures to natural stimuli can give rise to the rapid encoding of new episodic memories. On the one hand, human studies have not addressed episodic memory formation at the single neuron level. In spite of the major significance of these works in advancing our understanding of episodic memory, their contribution has been limited. Furthermore, neurophysiological and lesion studies in animals have shown that the MTL is involved in the encoding of associations ( Bunsey and Eichenbaum, 1996 Day et al., 2003 Kahana et al., 2008 Sakai and Miyashita, 1991 Wirth et al., 2003), which is a key mechanism for episodic memory formation. Neuroimaging investigations in humans and behavioral studies of neurological patients have substantiated the importance of the medial temporal lobe (MTL) for episodic memories ( Davachi, 2006 Eichenbaum, 2004 Eichenbaum et al., 2007 Moscovitch, 1994 Squire et al., 2004 Tulving, 2002).