Hippocampal declarative memory supports gesture production: Evidence from amnesia

Abstract

Spontaneous co-speech hand gestures provide a visuospatial representation of what is being communicated in spoken language. Although it is clear that gestures emerge from representations in memory for what is being communicated (De Ruiter, 1998; Wesp, Hesse, Keutmann, & Wheaton, 2001), the mechanism supporting the relationship between gesture and memory is unknown. Current theories of gesture production posit that action – supported by motor areas of the brain – is key in determining whether gestures are produced. We propose that when and how gestures are produced is determined in part by hippocampally-mediated declarative memory. We examined the speech and gesture of healthy older adults and of memory-impaired patients with hippocampal amnesia during four discourse tasks that required accessing episodes and information from the remote past. Consistent with previous reports of impoverished spoken language in patients with hippocampal amnesia, we predicted that these patients, who have difficulty generating multifaceted declarative memory representations, may in turn have impoverished gesture production. We found that patients gestured less overall relative to healthy comparison participants, and that this was particularly evident in tasks that may rely more heavily on declarative memory. Thus, gestures do not just emerge from the motor representation activated for speaking, but are also sensitive to the representation available in hippocampal declarative memory, suggesting a direct link between memory and gesture production.

The influence of the hippocampus and declarative memory on word use: Patients with amnesia use less imageable words

“…For example, there are a number of other works that specifically implicate hippocampal declarative memory in contributing to language use. Patients with amnesia gesture at lower rates when describing past events (Hilverman et al, 2016) and are impaired at producing definite reference (e.g., the angle vs. an angle) to explicitly signal that something is mutually known (Duff et al, 2011). These are examples where disruptions in language use are most parsimoniously interpreted as resulting from impoverished declarative memory representations.…”

“…Despite these demonstrations of hippocampal involvement in language processing, it is unknown if these disruptions following hippocampal damage and declarative memory impairment extend to the individual words used to describe representations in memory. Exploratory analyses conducted on a previously published data set suggested that this was the case (Hilverman et al, 2016). Accordingly, we tested this hypothesis by examining the imageability and concreteness of words used in a narrative task by amnesic patients and comparison participants.…”

“…Hippocampal amnesic patients have a range of sentence and discourse level deficits in both production and in comprehension (e.g., Duff and Brown-Schmidt, 2012; 2017; MacKay et al, 1998), even extending to nonverbal aspects of language: amnesic patients gesture less than healthy comparison participants during narrative production (Hilverman et al, 2016). Hippocampal functioning has also been linked to semantic processing and knowledge.…”

The intersection between the oculomotor and hippocampal memory systems: empirical developments and clinical implications

“…Concerning the former, further research is needed to comprehensively understand how varied information from distinct neural regions are prioritized within a priority map in the guidance of oculomotor behavior . Concerning the latter, models of hippocampal function do not often consider the structural and functional intersections with the effector systems that govern overt behavior, even though decades of research has looked to changes in overt behavior (e.g., response times, actions, and gestures) to make inferences about the influence of memory . A paradigm shift may be needed in memory research: studying the nature of encoding or retrieval, including its underlying neural dynamics, without considering how information from the external world is integrated across movements of an effector system (here, gaze fixations), or how stored knowledge guides further exploration behaviors, may provide a limited view on how memories develop and are used.…”

SyNoPsis: Disruptive Innovation for Mapping Schizophrenia onto the Brain

“…The authors have pioneered the scientific study of hand gestures in psychotic patients. Will they map this behavior onto the motor system or will they also consider an important role of the memory system [5]?…”