Newborn’s brain activity signals the origin of word memories

Abstract

Recent research has shown that specific areas of the human brain are activated by speech from the time of birth. However, it is currently unknown whether newborns' brains also encode and remember the sounds of words when processing speech. The present study investigates the type of information that newborns retain when they hear words and the brain structures that support word-sound recognition. Forty-four healthy newborns were tested with the functional near-infrared spectroscopy method to establish their ability to memorize the sound of a word and distinguish it from a phonetically similar one, 2 min after encoding. Right frontal regions-comparable to those activated in adults during retrieval of verbal materialshowed a characteristic neural signature of recognition when newborns listened to a test word that had the same vowel of a previously heard word. In contrast, a characteristic novelty response was found when a test word had different vowels than the familiar word, despite having the same consonants. These results indicate that the information carried by vowels is better recognized by newborns than the information carried by consonants. Moreover, these data suggest that right frontal areas may support the recognition of speech sequences from the very first stages of language acquisition.neonate's memory | right frontal lobe | sound encoding | speech perception | oxyhemoglobin P revious studies have shown that newborns and human fetuses are able to remember word sounds (1-3) as well as to extract prosodic properties of speech (4) or identity relations between syllables (5, 6). However, neither the specific elements newborns encode from speech, nor the brain structures that mediate speech recognition at birth have been precisely characterized. Building on a functional near-infrared spectroscopy (fNIRS) paradigm used to test memory in newborns (7), the present study asks whether the newborn can remember all of the sounds [consonants (C) and vowels (V)] that form a bisyllabic CVCV word, or whether some of these segments are better encoded than others.Judging by the number of studies reporting early abilities to discriminate fine phonetic contrasts (8), one might be inclined to ascribe to newborns a very detailed representation of the sound of words. In fact, newborns appear to discriminate all phonetic contrasts of the languages of the world, including those that their parents can no longer distinguish. Newborns distinguish consonants differing in one feature-for example, place of articulation, voicing, manner of articulation (9-11), duration (12)-as well as vowel quality contrasts (13,14). Do the representations newborns hold in memory contain the full range of segmental details suggested by these discrimination capacities?Different studies suggest that in adults (15-18), and in infants older than 12 mo (19-23), consonantal sequences are encoded more robustly than vocalic sequences for the representation of words. It is possible that a similar bias (namely, preference for consonantal information when encodi...

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

“…Consistently with the pattern observed in the RF region and in previous memory studies in newborns (10,11), the response of the novel-word group was greater than the response of the same-word group.…”

“…The differential brain activations between the same-word group and the novel-word group in the recognition test (firstly and most strongly in RF areas) closely resemble those observed in previous studies addressing word memory in newborns (10,11). It is hard to disentangle, from these findings, whether the RF region is implicated in recognizing "novel features" (thus the increment of the OxyHb in the novel-word group) or "familiar features" (reflected in the decrement of the OxyHb in the same-word group).…”

“…Developmental studies in the language domain have uncovered basic perceptual (4-6), discrimination (7,8), and mnemonic capacities (9)(10)(11)(12)(13)(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.…”

“…Frontal and parietal regions are believed to sustain important domain-general functions from early infancy (29). Frontal regions are functionally involved in memory tasks (11,30,31), novelty and invariance detection (32,33), and attentional orienting (33)(34)(35). Parietal regions have connections with the frontal regions and have also been associated with mnemonic (36,37), attentional (38), and verbal working memory processes in adults (39,40).…”

Mother’s voice and heartbeat sounds elicit auditory plasticity in the human brain before full gestation

“…Previous research suggests that the innate preference for mother's voice shapes the developmental trajectory of the brain (10,11). Prenatal exposure to mother's voice may therefore provide the brain with the auditory fitness necessary to process and store speech information immediately after birth (12,13).…”