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

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 4 h 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

Degree of learning of an artificial grammar correlates with differential fMRI activation of Broca's area

The relevance of Broca's area to language grammar processing is well established. Its relevance to implicitly learned non-linguistic sequential rules has also been demonstrated. Previous work by our lab has shown this is true even if subjects are unaware they are being trained on, and tested for, sensitivity to these rules. We extend this work to show that the degree of differential activation in Broca's area for implicitly learned grammatical vs. ungrammatical sequences is correlated across subjects with behavioral evidence of their degree of learning of these rules (as assessed by reaction time differences). Broca's is among the three regions showing the highest association with degree of learning. This finding further underscores the relevance of Broca's for non-linguistic rule learning, and suggests that the original function of this area in our pre-human ancestors may have been the implicit learning of any kind of sequential patterns in the environment

Stone tools and trained brains: Comparing anatomical connectivity in expert toolmakers versus naïve subjects using Diffusion Tensor Imaging

Our study gathered Diffusion Tensor Imaging data to compare anatomical connectivity in expert stone toolmakers with naïve subjects with no prior toolmaking experience. The introduction of stone tool technology marked a shift in the evolution of human cognition, as early hominins gradually developed their capacity for complex hierarchical action planning and coordination. It is hypothesized that other abilities requiring these same capacities, like language, co-opted this neurocognitive scaffolding. Similarities in connectivity between experts and novices thus may be explained by the involvement of these networks in language or by a ubiquitous human competence in everyday tool use. Differences are likely explained by the increased complexity of the tool types experts make and use. These differences would support findings from a previous analysis within this study that found tool types of varying complexity (Oldowan, Acheulean, Levallois) differentially activated language networks for subjects with different levels of expertise