Concept cells: the building blocks of declarative memory functions

“…the hierarchical structure of the MTL: 52% of the neurons show visual invariance in PHC versus 85% in the hippocampus, and while no neuron in PHC showed responses to the text or sound presentations, about half the neurons did so in the hippocampus (Quian Quiroga 2012b; Quian Quiroga et al., 2009).”

“…connections from cortex to hippocampus or amygdala were more direct than their outgoing counterparts, is in keeping with this view of the hippocampus and amygdala as integrators of the activity of widely distributed cortical networks (Felleman and Van Essen, 1991; Mesulam, 1998; Quiroga, 2012).”

“Indeed, many studies fi nd evidence that humans integrate modality-speci fi c information into multimodal representations [95,96].”

“VS cells are reproducible across tasks, recording techniques, and laboratories [35–39,41–43] (see [41] for a review) and their responses are abstract and”

“The particular design and task set used in this experiment also reflect a targeted combination of MTL related functions, including having representations related to concepts (Quiroga, 2012) and to spatial navigation (Moser et al., 2017).”

“Neurons with some properties like those of human concept cells (Quian Quiroga, 2023) are found in nonhuman primates, but clearly with language in humans concept cells can be much more elaborate.”

“In the human MTL it has been shown the existence of neurons with selective and invariant responses that represent the meaning of the stimulus for declarative memory functions [47,48].”

“Moreover, some neurons can exhibit remarkable selectivity to complex stimuli, the evidence that has led to debates around the existence of the so-called “grand mother” and “concept” cells (Quiroga et al. 2005;Viskontas et al. 2009;Quiroga 2012), and their role as elements of a declarative memory.”

“A representation where individual neurons are selectively sensitive to high-level features (Section ‘Feature selectivity’) is a step toward the ‘concept’ representations found at the final stage of cortical processing [2,76].”

“Notwithstanding, such selective and explicit response behavior is consistent with observations from single-neuron recordings in medial temporal cortex in humans (Földiák, 2009; Quian Quiroga, 2012).”

“Extreme selectivity of biological neurons High separation capabilities of linear functionals (Theorems 1–3, Remark 3) may shed light on the puzzle associated with the so-called Grandmother [39], [49] or Concept cells [38] in neuroscience.”

“Recordings from epilepsy patients have revealed neurons that respond sparsely to just one of many possible concepts, like "Bill Clinton" [57].”

“These ATL cells do appear to contribute substantially to our conceptual knowledge of well-known people and places; indeed, that is why Quiroga (2012) calls them “concept cells.””

“Quiroga (2012) has shown that humans have “concept neurons.””

“These cells were discovered in patients suffering from intractable epilepsy during their evaluation for surgical removal of the epileptic focus (Quian Quiroga 2012; Quian Quiroga and others 2009).”

“For instance, Quiroga et al [16] found a neuron that responded selectively when a person viewed images of the television host Oprah Winfrey, viewed her written name, or heard her spoken name.”

“In particular, researchers have reported on a remarkable subset of MTL neurons that are selectively activated by strikingly different pictures of given individuals, landmarks or objects and in some cases even by letter strings with their names [28].”

“Moreover, the same neuron responded to the name of that person expressed in different modalities (written and spoken) [134].”

“This rare approach in humans [253] has led to highly original observations - such as the so-called ‘concept cells’ firing to multimodal inputs related to people, places, or events in the human medial temporal lobe [254,255].”

“It was about 100 ms slower than in the more posterior clusters S2–4, which agrees with the differences in response latency reported for single-unit hippocampal activity (Mormann et al., 2008; Quiroga, 2012).”

“This last point, in particular, might have significantly affected our results because of the known sparse coding properties of the hippocampus (e.g., Treves & Rolls 1994; Quiroga 2012), that does not guarantee that voxels showing hierarchical structures across participants will correspond after normalization.”

“The SI units and MI units identi fi ed in the present study are also reminiscent of the concept cells of the exemplar-based model 7 .”

“New approaches to cognitive neuroscience One of the most basic principles of brain function is that the brain processes very little information and infers the rest based on assumptions [17].”

“, by responding to a particular celebrity across different images as well as to the celebrity’s name presented in text (Quiroga et al., 2005; Quiroga, 2012).”

“In fact, the opposite is often the case, as some of these neurons tend to fire to more than one concept (Quian Quiroga et al. 2009, Quian Quiroga and Kreiman 2010a, Quian Quiroga 2012).”

“…and distributed code where many cells respond to a specific concept, and related concepts will active a partially overlapping population of cells (Quian Quiroga, 2016, 2012), giving rise to a distributed spatial pattern where the degree of overlapping cells could relate to conceptual overlap.”

“A striking example comes from Quiroga (2012) who argued that human brains contain “concept” cells which are involved in the representation of individual people or objects regardless of the modality used to sense those people or objects.”

“Ourresults areinlinewiththeideathatconceptcellsrepresentthebuildingblocks of memory 40 .”

“Hippocampal activity has been linked to the representation of event associations (Mack, Love, & Preston, 2017; Quiroga, 2012; Quiroga, Reddy, Kreiman, Koch, & Fried, 2005; Ekstrom et al., 2003).”

“Inspired by the previous research work, an invariant, sparse, and explicit code, which might be important in the transformation of complex visual percepts into long-term and more abstract memories (Quiroga, 2012).”

“This hierarchical organization is accompanied by an increase in abstraction, so that neural responses in higher tier regions are highly invariant to lowlevel sensory properties and increasingly sensitive to properties that characterize identity and semantics (for review see (Quiroga, 2012)).”

“…macaque temporal lobe, but on the basis of many such recordings, those who have recorded these neurons argue that the code is sparsely distributed (Quiroga, 2012, 2013; Quiroga, Kreiman, Koch, & Fried, 2008; Rey et al., 2015), and therefore somewhat similar to that of neurons in macaques (Rolls &…”

“, 2003; Wirtshafter & Wilson, 2019), and, in humans, even abstract concepts (Bausch et al., 2021; Quiroga, 2012; Suthana et al., 2015)] in different environments (Schimanski et al.”

“Sparse coding has been commonly observed in the hippocampus, where as few as 50 to 200 cells may participate in the encoding of a single representation [19, 20].”

“Arguments for the existence of high-level ‘object neurons’ were made by several researchers [2–6].”

“He arrived at a set of 1020 sentences (see Pinker 1994).”

“One of the first of such neurons was called the Jennifer Aniston neuron, as it responded selectively to different pictures of the actress Jennifer Aniston [12,24].”

“…of these networks, achieving an interpretable understanding of how local computational elements coordinate to address global tasks is challenging and remains an ongoing focus of intense research for both BNNs (Dumont et al., 2023; Quiroga, 2012) and ANNs (Räuker et al., 2023; Angelov et al., 2021).”

“The ability to focus on what to discard, what is not relevant, is becoming more relevant not only in cognitive science and neuroscience (Quiroga, 2012), but also in AI (e.”

“These neurons have been collectively named “Jennifer Aniston cells” or “concept cells” (Quiroga, 2012; Quiroga et al., 2005).”

“medial temporal lobe (MTL) neurons that are selectively activated by strikingly different pictures of given individuals, landmarks or objects and in some cases even by letter strings with their names [95, 94]. For example, neurons have been shown to selectively respond to famous actors like “Halle Berry”. Thus a local…”

“The concept model is supported by human singleneuron studies showing that hippocampal neurons respond highly selectively to specific persons or objects, regardless of visual appearances or stimulus modalities (Quian Quiroga, 2012; Quian Quiroga et al., 2005, 2008).”

“Concept formation may occur in the hippocampus, amygdala, or entorhinal cortex (Quiroga, 2012).”

“The development of neuroscience has put forward high requirements for analyzing neural activity at both single neuron [1-4] and population levels [5-7].”

“a concept neuron in the human brain [42]”

“A different but related line of research is based on intra-cranial recordings of neuronal activity conducted in patients called ‘concept cells’ (Quiroga, 2012; Quiroga, Fried, & Koch, 2013).”

“Of importance, the previous two studies employed images that are known to produce semantic memory–a type of long-term memory–activity in the hippocampus (Quiroga, 2012).”

“It has been proposed that single neurons can underlie very specific and abstract item representations or concepts and, thus, may form the building blocks for human declarative memory [18], [19], but recent work points to sparsely distributed neuronal populations [20], [21] as the substrate of encoded information.”

“This sparse and hierarchical structure reduces the model complexity and DCH pursues a parse modular hierarchical structure, as found in human brains (Quiroga 2012).”

“Overall, the hippocampus is known to play a role in learning features and their associations over multiple dimensions, ranging from spatial location encoding (E. I. Moser, Kropff and Moser, 2008) to semantic relationships (Solomon et al., 2019) to abstract concepts (Quiroga, 2012).”

“The existence of ‘concept cells’ in the hippocampus, which respond similarly to different instantiations of a given concept (e.g., ‘Jennifer Aniston’ [10]), could be taken as evidence that the hippocampus does store remote semantic memories.”

“A uniquely human single-neuron correlate of memory items is represented by concept neurons in the MTL, which selectively and invariantly respond to stimuli containing a preferred semantic concept 8 (for example, our friend).”

“Multimodal semantic representations of these types, perhaps formed in the way described here, are, it is suggested, what “concept cells” recorded in humans (Quian 2012) and perhaps in non-human primates (Rolls 2023c) reflect.”

“However, it should also be noted that in the medial temporal lobe, researchers (e.g., Quiroga, 2012) identified single neurons called “concept cells,” capable of responding selectively and abstractly to specific people and objects (such as Jennifer Aniston or the Tower of Pisa).”

“However, while these neurons have been defined as “concept cells”, they are thought to play a role in creation of associations and recollection of (recent or recently refreshed) conscious episodic memory events rather than supporting long-term semantic associations [25].”

“Given the many T leads responding in a task using only very basic categories, the category label is likely distributed over large numbers of neurons, unlike what has been reported for declarative memory 42 .”

“Notably, however, in the MTL so far only 2 exemplar-based coding has been demonstrated (13, 14).”