Decoding the Formation of New Semantics: MVPA Investigation of Rapid Neocortical Plasticity during Associative Encoding through Fast Mapping

Abstract

Neocortical structures typically only support slow acquisition of declarative memory; however, learning through fast mapping may facilitate rapid learning-induced cortical plasticity and hippocampal-independent integration of novel associations into existing semantic networks. During fast mapping the meaning of new words and concepts is inferred, and durable novel associations are incidentally formed, a process thought to support early childhood's exuberant learning. The anterior temporal lobe, a cortical semantic memory hub, may critically support such learning. We investigated encoding of semantic associations through fast mapping using fMRI and multivoxel pattern analysis. Subsequent memory performance following fast mapping was more efficiently predicted using anterior temporal lobe than hippocampal voxels, while standard explicit encoding was best predicted by hippocampal activity. Searchlight algorithms revealed additional activity patterns that predicted successful fast mapping semantic learning located in lateral occipitotemporal and parietotemporal neocortex and ventrolateral prefrontal cortex. By contrast, successful explicit encoding could be classified by activity in medial and dorsolateral prefrontal and parahippocampal cortices. We propose that fast mapping promotes incidental rapid integration of new associations into existing neocortical semantic networks by activating related, nonoverlapping conceptual knowledge. In healthy adults, this is better captured by unique anterior and lateral temporal lobe activity patterns, while hippocampal involvement is less predictive of this kind of learning.

Small Sets of Novel Words Are Fully Retained After 1-Week in Typically Developing Children and Down Syndrome: A Fast Mapping Study

“…Compared to the EE condition, the FM condition had significantly increased activity in the anterior temporal lobe (ATL). This finding, in concert with a similar study (Atir-Sharon et al, 2015) suggests that an ATL-related network is responsible for associations learned through FM. In total, these studies provide a potential alternative learning strategy for novel arbitrary associations mediated by the ATL.…”

Impaired acquisition of new words after left temporal lobectomy despite normal fast-mapping behavior

“…On this topic, Sharon et al (2011) reported one case (patient K.S.) with relatively focal left temporal pole damage who had word learning impairments despite fast-mapping study, and functional neuroimaging studies have provided correlational evidence consistent with that perspective (Atir-Sharon et al, 2015; Merhav et al, 2015). Returning to the current patient sample, the history of epilepsy shared by all TL participants could potentially have contributed to deficits in name learning.…”

“…The large number of component processes will make it challenging to identify regions that might be uniquely associated with and necessary for fast-mapping behavior. Candidate regions might be identified based on correlational functional neuroimaging data related to word learning and fast mapping performance (Atir-Sharon, Gilboa, Hazan, Koilis, & Manevitz, 2015; Davis et al, 2009; Merhav, Karni, & Gilboa, 2015), and those candidate regions could be evaluated neuropsychologically.…”

Feature overlap modulates rapid semantic but not lexical integration of novel associations by means of fast mapping

“…However, there are studies in which these criteria were entirely fulfilled but still, no 1 This does not necessarily mean that learning by means of FM is always hippocampus-independent. It has been shown that the hippocampus contributes to FM learning in healthy young adults (Atir-Sharon, Gilboa, Hazan, Koilis, & Manevitz, 2015) or at least it cannot finally be excluded that it is not involved (Merhav et al, 2015). We propose that in patients with severe and selective hippocampal lesions it is valid to conclude that hippocampal activity cannot have contributed to FM learning or retrieval.…”

“…Contrary to previous studies (cf. Atir- Sharon et al, 2015;Coutanche & Thompson-Schill, 2014;Greve et al, 2014;Himmer et al, 2017;Korenic et al, 2016;Merhav et al, 2014Merhav et al, , 2015Sharon et al, 2011;Smith et al, 2014;Warren & Duff, 2014;Warren et al, 2016), the EE group was presented with the same questions as the FM groups, in order to prevent any confounds due to inconsistencies in task demands apart from the critical FM determinants. Before the actual experiment started, all three groups conducted a practice phase of six encoding trials.…”