Prefrontal cortex activation supports the emergence of early stone age toolmaking skill

Abstract

Trends toward encephalization and technological complexity ~1.8 million years ago may signify cognitive development in the genus Homo. Using functional near-infrared spectroscopy, we measured relative brain activity of 33 human subjects at three different points as they learned to make replicative Oldowan and Acheulian Early Stone Age tools. Here we show that the more complex early Acheulian industry recruits left dorsolateral prefrontal cortex when skills related to this task are first being learned. Individuals with increased activity in this area are the most proficient at the Acheulian task. The Oldowan task, on the other hand, transitions to automatic processing in less than four hours of training. Individuals with increased sensorimotor activity demonstrate the most skill at this task. We argue that enhanced working memory abilities received positive selection in response to technological needs during the early Pleistocene, setting Homo on the path to becoming human.

The measurement, evolution, and neural representation of action grammars of human behavior

“…The conjunction of the two covariates reveals regions of left parietal operculum and rIFG ( pars opercularis) that are specifically responsive to stimulus complexity irrespective of measurement method. This is consistent with prior evidence of inferior frontoparietal functional activation 31 , 32 , 67 – 69 and structural remodeling 70 in response to stone tool making, which have previously been interpreted using informal, qualitative estimations of technological complexity and reverse inference from published studies of other tasks. Parameterization of complexity through grammar extraction now allows direct identification of activity driven by sequence structure and more specific localization to cognitive control 71 , 72 and multisensory integration 73 regions of inferior frontal and parietal cortex.…”

Action Grammars of Human Behavior – Measurement, Evolution, and Neural Representation

“…The conjunction of the two covariates reveals regions of left parietal operculum and rIFG (pars opercularis) that are specifically responsive to stimulus complexity irrespective of measurement method. This is consistent with prior evidence of inferior frontoparietal functional activation 31,32,[67][68][69] and structural remodeling 70 in response to stone tool making, which have previously been interpreted using informal, qualitative estimations of technological complexity and reverse inference from published studies of other tasks. Parameterization of complexity through grammar extraction now allows direct identification of activity driven by sequence structure and more specific localization to cognitive control 71,72 and multisensory integration 73 regions of inferior frontal and parietal cortex.…”

Semiotics and the Origin of Language in the Lower Palaeolithic

“…This proposed linkage between the complex nested routines of cleaver-making and the use of symbols (words) as scaffolds for managing the sequencing of tasks, complements neuroimaging research on shared networks for tool-making and language (Uomini and Meyer 2013;Meyer et al 2014;Stout et al 2015;Putt et al 2019), and the experimental studies showing the effectiveness of teaching with language in learning complex tool-making routines (Morgan et al 2015;Lombao et al 2017).…”