Saloni Krishnan

Neurobiological Basis of Language Learning Difficulties.

In this paper we highlight why there is a need to examine subcortical learning systems in children with language impairment and dyslexia, rather than focusing solely on cortical areas relevant for language. First, behavioural studies find that children with these neurodevelopmental disorders perform less well than peers on procedural learning tasks that depend on corticostriatal learning circuits. Second, fMRI studies in neurotypical adults implicate corticostriatal and hippocampal systems in language learning. Finally, structural and functional abnormalities are seen in the striatum in children with language disorders. Studying corticostriatal networks in developmental language disorders could offer us insights into their neurobiological basis and elucidate possible modes of compensation for intervention.

Roles of Supplementary Motor Areas in Auditory Processing and Auditory Imagery

Although the supplementary and pre-supplementary motor areas have been intensely investigated in relation to their motor functions, they are also consistently reported in studies of auditory processing and auditory imagery. This involvement is commonly overlooked, in contrast to lateral premotor and inferior prefrontal areas. We argue here for the engagement of supplementary motor areas across a variety of sound categories, including speech, vocalizations, and music, and we discuss how our understanding of auditory processes in these regions relate to findings and hypotheses from the motor literature. We suggest that supplementary and pre-supplementary motor areas play a role in facilitating spontaneous motor responses to sound, and in supporting a flexible engagement of sensorimotor processes to enable imagery and to guide auditory perception.

Functional and Quantitative MRI Mapping of Somatomotor Representations of Human Supralaryngeal Vocal Tract.

Abstract Speech articulation requires precise control of and coordination between the effectors of the vocal tract (e.g., lips, tongue, soft palate, and larynx). However, it is unclear how the cortex represents movements of and contact between these effectors during speech, or how these cortical responses relate to inter‐regional anatomical borders. Here, we used phase‐encoded fMRI to map somatomotor representations of speech articulations. Phonetically trained participants produced speech phones, progressing from front (bilabial) to back (glottal) place of articulation. Maps of cortical myelin proxies (R1 = 1/T1) further allowed us to situate functional maps with respect to anatomical borders of motor and somatosensory regions. Across participants, we found a consistent topological map of place of articulation, spanning the central sulcus and primary motor and somatosensory areas, that moved from lateral to inferior as place of articulation progressed from front to back. Phones produced at velar and glottal places of articulation activated the inferior aspect of the central sulcus, but with considerable across‐subject variability. R1 maps for a subset of participants revealed that articulator maps extended posteriorly into secondary somatosensory regions. These results show consistent topological organization of cortical representations of the vocal apparatus in the context of speech behavior.

Convergent and Divergent fMRI Responses in Children and Adults to Increasing Language Production Demands

In adults, patterns of neural activation associated with perhaps the most basic language skill—overt object naming—are extensively modulated by the psycholinguistic and visual complexity of the stimuli. Do childrens brains react similarly when confronted with increasing processing demands, or they solve this problem in a different way? Here we scanned 37 children aged 7–13 and 19 young adults who performed a well-normed picture-naming task with 3 levels of difficulty. While neural organization for naming was largely similar in childhood and adulthood, adults had greater activation in all naming conditions over inferior temporal gyri and superior temporal gyri/supramarginal gyri. Manipulating naming complexity affected adults and children quite differently: neural activation, especially over the dorsolateral prefrontal cortex, showed complexity-dependent increases in adults, but complexity-dependent decreases in children. These represent fundamentally different responses to the linguistic and conceptual challenges of a simple naming task that makes no demands on literacy or metalinguistics. We discuss how these neural differences might result from different cognitive strategies used by adults and children during lexical retrieval/production as well as developmental changes in brain structure and functional connectivity.

Distinct processing of ambiguous speech in people with non-clinical auditory verbal hallucinations

&NA; Auditory verbal hallucinations (hearing voices) are typically associated with psychosis, but a minority of the general population also experience them frequently and without distress. Such ‘non‐clinical’ experiences offer a rare and unique opportunity to study hallucinations apart from confounding clinical factors, thus allowing for the identification of symptom‐specific mechanisms. Recent theories propose that hallucinations result from an imbalance of prior expectation and sensory information, but whether such an imbalance also influences auditory‐perceptual processes remains unknown. We examine for the first time the cortical processing of ambiguous speech in people without psychosis who regularly hear voices. Twelve non‐clinical voice‐hearers and 17 matched controls completed a functional magnetic resonance imaging scan while passively listening to degraded speech (‘sine‐wave’ speech), that was either potentially intelligible or unintelligible. Voice‐hearers reported recognizing the presence of speech in the stimuli before controls, and before being explicitly informed of its intelligibility. Across both groups, intelligible sine‐wave speech engaged a typical left‐lateralized speech processing network. Notably, however, voice‐hearers showed stronger intelligibility responses than controls in the dorsal anterior cingulate cortex and in the superior frontal gyrus. This suggests an enhanced involvement of attention and sensorimotor processes, selectively when speech was potentially intelligible. Altogether, these behavioural and neural findings indicate that people with hallucinatory experiences show distinct responses to meaningful auditory stimuli. A greater weighting towards prior knowledge and expectation might cause non‐veridical auditory sensations in these individuals, but it might also spontaneously facilitate perceptual processing where such knowledge is required. This has implications for the understanding of hallucinations in clinical and non‐clinical populations, and is consistent with current ‘predictive processing’ theories of psychosis.

Fractionating nonword repetition: The contributions of short-term memory and oromotor praxis are different.

The ability to reproduce novel words is a sensitive marker of language impairment across a variety of developmental disorders. Nonword repetition tasks are thought to reflect phonological short-term memory skills. Yet, when children hear and then utter a word for the first time, they must transform a novel speech signal into a series of coordinated, precisely timed oral movements. Little is known about how children’s oromotor speed, planning and co-ordination abilities might influence their ability to repeat novel nonwords, beyond the influence of higher-level cognitive and linguistic skills. In the present study, we tested 35 typically developing children between the ages of 5−8 years on measures of nonword repetition, digit span, memory for non-verbal sequences, reading fluency, oromotor praxis, and oral diadochokinesis. We found that oromotor praxis uniquely predicted nonword repetition ability in school-age children, and that the variance it accounted for was additional to that of digit span, memory for non-verbal sequences, articulatory rate (measured by oral diadochokinesis) as well as reading fluency. We conclude that the ability to compute and execute novel sensorimotor transformations affects the production of novel words. These results have important implications for understanding motor/language relations in neurodevelopmental disorders.

Williams syndrome: A surprising deficit in oromotor praxis in a population with proficient language production

Williams Syndrome (WS) is a neurodevelopmental disorder of known genetic origin, characterized by serious delays in language onset yet relatively verbose, intelligible and fluent speech in late childhood and adulthood. How do motor abilities relate to language in this group? We investigated planning and co-ordination of the movement of the speech articulators (oromotor praxis) in 28 fluent-speaking individuals with WS, aged between 12 and 30 years. Results indicate that, despite their fluent language, oromotor praxis was impaired in WS relative to two groups of typically-developing children, matched on either vocabulary or visuospatial ability. These findings suggest that the ability to plan, co-ordinate and execute complex sensorimotor movements contribute to an explanation of the delay in expressive language early in development in this neurodevelopmental disorder. In the discussion, we turn to more general issues of how individual variation in oromotor praxis may account for differences in speech/language production abilities across developmental language disorders.

The effect of recall, reproduction, and restudy on word learning: a pre-registered study

BackgroundCertain manipulations, such as testing oneself on newly learned word associations (recall), or the act of repeating a word during training (reproduction), can lead to better learning and retention relative to simply providing more exposure to the word (restudy). Such benefit has been observed for written words. Here, we test how these training manipulations affect learning of words presented aurally, when participants are required to produce these novel phonological forms in a recall task.MethodsParticipants (36 English-speaking adults) learned 27 pseudowords, which were paired with 27 unfamiliar pictures. They were given cued recall practice for 9 of the words, reproduction practice for another set of 9 words, and the remaining 9 words were restudied. Participants were tested on their recognition (3-alternative forced choice) and recall (saying the pseudoword in response to a picture) of these items immediately after training, and a week after training. Our hypotheses were that reproduction and restudy practice would lead to better learning immediately after training, but that cued recall practice would lead to better retention in the long term.ResultsIn all three conditions, recognition performance was extremely high immediately after training, and a week following training, indicating that participants had acquired associations between the novel pictures and novel words. In addition, recognition and cued recall performance was better immediately after training relative to a week later, confirming that participants forgot some words over time. However, results in the cued recall task did not support our hypotheses. Immediately after training, participants showed an advantage for cued Recall over the Restudy condition, but not over the Reproduce condition. Furthermore, there was no boost for the cued Recall condition over time relative to the other two conditions. Results from a Bayesian analysis also supported this null finding. Nonetheless, we found a clear effect of word length, with shorter words being better learned than longer words, indicating that our method was sufficiently sensitive to detect an impact of condition on learning.ConclusionsOur primary hypothesis about training conditions conferring specific advantages for production of novel words presented aurally, especially over long intervals, was not supported by this data. Although there may be practical reasons for preferring a particular method for training expressive vocabulary, no difference in effectiveness was detected when presenting words aurally: reproducing, recalling or restudying a word led to the same production accuracy.

Chapter 89 – Environmental Sounds

How are environmental sounds relevant to the neurobiology of language? As studied in the 20th century, the purported structure of language and its processing—a human-specific “faculty” characterized by an abstract system of rules governing the hierarchical recombination of symbols encoded by arbitrary sound units—is seemingly unrelated to the recognition and comprehension of environmental sounds. Environmental sounds have often been used as a means of defining what is “language-specific” in the brain. However, as research in both language and environmental sounds has matured, useful parallels between the two domains have emerged, as well as some illustrative differences. In this chapter, we first discuss what environmental sounds are (and are not), and then move through different aspects of environmental sounds research that parallel fields of study in language. We consider, in detail, the behavioral and neuroimaging evidence for how environmental sounds are processed, highlighting the range of perceptual, cross-modal, semantic, and contextual processes involved, and finish by considering how studying environmental sounds informs our understanding of language processing.

What Have We Learned About Learning? Reflections from Developmental Psychology and Cognitive Neuroscience

Learning is thought to be something at which human beings excel. They learn many things over the course of time from infancy to adulthood, such as how to communicate with others using language, how to manipulate objects, and how to solve problems effectively. But what is the science behind learning? How do people’s brains change as they learn, and does this have anything to do with the strategies they use to learn? In this essay, we briefly outline the changes in how researchers approach the issue of learning across development, with a focus on language learning, and discuss how current neuroscientific research complements what is known behaviorally about learning. We illustrate how various developmental and neural processing inputs interact with prior experience to facilitate learning. Further, the contributions of active learning over the lifespan, and the roles of novelty and motivation in enhancing learning, are considered. Approaching learning as a complex, multifaceted process will help researchers move toward more-integrated behavioral and neurobiological models of learning.