Motor and attentional development

Brain organization for motor behavior Similar to organization for sensation Brain sends signals through thalamus, down spinal chord, controlling movements of limbs etc. Involves long axons, myelination is important

Motor development Reflexes Reflexes usually involve little or no cortical activity Some reflexes only go as far as synapses in spinal cord Others go to brainstem, still others to cortex Reflexes that are present in babies are probably mostly subcortical or spinal cord types Why might reflexes be beneficial to babies?

Motor control Requires 2 things Stability Flexibility

Coordination Basal Ganglia Cerebellum

Reaching Reaching in adults is both stable (can be repeated easily) and flexible (adults can reach to any location These abilities develop gradually in infants First infant develop general reaching abilities Infants will grab things put into their hands, but will only voluntarily reach beginning at about 4 months. Flexibility occurs with practice at reaching How might plasticity relate to these developments?

Infants also perseverate – once they are able to reach, they often are unable to stop reaching – Why? Possibly development of inhibition Possibly memory or control over actions

Other motor behaviors Locomotion Motor Planning Development is probably related to several factors Strength Balance Control over limbs – myelin Motor Planning Involves areas other than primary motor cortex These areas probably mature much later

Attention Richards has measured attention development in very young babies. Rothbart and Posner have proposed that there are multiple attention systems in the human brain, and that they develop on different schedules

Early attention A general arousal system likely develops early Four phases of attention Automatic interrupt Orienting response Sustained attention Termination of attention Heart rate varies with phase of attention Decreases during orienting and sustained attention

Sustained attention Visual fixation Lack of response to peripheral stimuli Decreased heart rate Sustained attention and changes in sustained attention may relate to cognitive development.

Orienting Networks Covert orienting Develops fairly early Visual areas including frontal eye fields Interactions with parietal lobes Visual cortex Basal Ganglia Develops fairly early Novelty – infants prefer to look at something new – may be subcortical Infants can engage attention with an interesting stimulus early in life, but once they’re fixated, it’s hard to break away.

Alerting Vigilance Both orienting and alerting probably rely on posterior and “low level” brain systems Parietal lobes Thalamus Frontal eye fields

Executive Control Involves more voluntary attention, most likely is late to develop (around 2 years) May be related to performance on cognitive tasks (e.g., reversal tasks, hiding tasks) Has also been implicated in more general development (e.g., social attention). Individual differences may relate to temperament – more excitable children may have a harder time disengaging, and may be more reactive.

Language Development Issues: Phonological Development Vocabulary Grammar Pragmatics