Brain regions and functional interactions supporting early word recognition in the face of input variability

Abstract

Perception and cognition in infants have been traditionally investigated using habituation paradigms, assuming that babies' memories in laboratory contexts are best constructed after numerous repetitions of the very same stimulus in the absence of interference. A crucial, yet open, question regards how babies deal with stimuli experienced in a fashion similar to everyday learning situationsnamely, in the presence of interfering stimuli. To address this question, we used functional near-infrared spectroscopy to test 40 healthy newborns on their ability to encode words presented in concomitance with other words. The results evidenced a habituation-like hemodynamic response during encoding in the left-frontal region, which was associated with a progressive decrement of the functional connections between this region and the left-temporal, right-temporal, and right-parietal regions. In a recognition test phase, a characteristic neural signature of recognition recruited first the right-frontal region and subsequently the right-parietal ones. Connections originating from the right-temporal regions to these areas emerged when newborns listened to the familiar word in the test phase. These findings suggest a neural specialization at birth characterized by the lateralization of memory functions: the interplay between temporal and left-frontal regions during encoding and between temporo-parietal and right-frontal regions during recognition of speech sounds. Most critically, the results show that newborns are capable of retaining the sound of specific words despite hearing other stimuli during encoding. Thus, habituation designs that include various items may be as effective for studying early memory as repeated presentation of a single word.newborns | language | habituation | memory | fNIRS effective connectivity H abituation, namely the decreased response to repeated presentations of stimuli, has been widely used to investigate infant cognition. Both behavioral (1) and neuroimaging (2, 3) habituation paradigms are regularly implemented for assessing a wide range of mental processes including categorization, object representation, and memory in very young babies. Despite this long tradition, it remains elusive the extent to which the results of habituation studies (which often consist of massive repetition of a single stimulus) can inform our understanding of memory functions in everyday-like situations-that is, in the presence of various stimuli.Developmental studies in the language domain have uncovered basic perceptual (4-6), discrimination (7,8), and mnemonic capacities (9-14) in newborns and fetuses, supporting the hypothesis that memories for sounds begin to be established very early in life. However, infants' memory for specific words seems to be highly vulnerable to interference. Newborns are capable of remembering a single word that they have heard in a classic habituation paradigm (i.e., consecutive/massed repetitions) and after a silent pause but readily forget the word if interfering words are introduced in the...

Sleeping neonates track transitional probabilities in speech but only retain the first syllable of words

“…Notably, whereas the superior temporal regions are affected by the immediate repetition of a sentence 54 , repetition at a longer time-scale of 14 s produces activation in the inferior frontal gyrus in three-month-old infants 55 . Moreover, a NIRS study in sleeping neonates revealed that a correlated activity between left-temporal and left-frontal regions, compatible with activation in the dorsal linguistic pathway, is crucial for word learning 56 . As for the hippocampus, activity has been reported in infants as young as 3-months when performing a visual sequence learning task, with no modulation by infant’s age 57 .…”

Habituation and novelty detection fNIRS brain responses in 5‐ and 8‐month‐old infants: The Gambia and UK

“…The fNIRS arrays were designed so that responses could be recorded over auditory associative brain regions including the inferior frontal gyrus (IFG), middle and superior temporal regions and extending to the temporo‐parietal junction across both cohorts (Lloyd‐Fox et al, ). These regions have been previously linked with auditory repetition suppression and novelty detection in early infancy (Benavides‐Varela et al, ; Bouchon et al, ; Mahmoudzadeh et al, ; Nakano et al, ) and adulthood (Belin & Zatorre, ; Dehaene‐Lambertz et al, ), and subsequent recovery of response to novel speech (Benavides‐Varela et al, ; Bouchon et al, ; Dehaene‐Lambertz et al, ).…”

“…In this study infants were awake, and this paradigm was presented as part of a battery of other fNIRS tasks. Therefore the design of previous studies (Benavides‐Varela et al, ; Nakano et al, ) was adapted with the intention of (a) increasing data retention, (b) utilizing a situation more similar to everyday learning situations (Benavides‐Varela et al, ), (c) creating a paradigm that would be more appropriate for application in a noisier and variable environment such as that often encountered in low‐resource global health research contexts (Sabanathan et al, ) and (c) allowing the investigation of responses in participants across a broad age range from 0 to 24 months of age. The paradigm employed a naturalistically presented and engaging sentence, spoken by a culturally appropriate adult (i.e.…”

From computing transition probabilities to word recognition in sleeping neonates, a two-step neural tale

“…Notably, whereas the superior temporal regions are affected by the immediate repetition of a sentence (Dehaene-Lambertz, 2017), repetition at a longer time-scale of 14 seconds produces activation in the inferior frontal gyrus in three-month-old infants (Dehaene-Lambertz et al, 2006). Moreover, a NIRS study in sleeping neonates revealed that a correlated activity between left-temporal and leftfrontal regions, compatible with activation in the dorsal linguistic pathway, is crucial for word learning (Benavides-Varela et al, 2017). As for the hippocampus, activity has been reported in infants as young as 3-months when performing a visual sequence learning task, with no modulation by infant's age (Ellis et al, 2020).…”