1. Part 1: Definitions, brain basis Isabelle Rapin
ATTENTION
Part 1: Definitions, brain basis Isabelle Rapin
Part 2: ADHD
Puja Patel
Seminar on Developmental Disorders
November 6, No conflict of interest

2. Connectivity networks
Defined functionally by
synchronous/coherent EEG rythmicity in distant neuronal areas
synchronous blood oxygen level dependent (BOLD) activation on fMRI
Defined anatomically by MRI visualization of myelinated pathways with diffusion tensor imaging (DTI)

3. Vigilance vs. Attention
Vigilance: state of arousal of the brain (midbrain RAF)
Attention to exogeneous stimuli: 2 major networks
Bottom-up = automatic orientation/response to salient sensory stimuli
Top-down = choice of response to sensory stimuli given on-going organismic priorities
Attention to endogeneous stimuli: default network (active both awake and in REM sleep; inactive in slow-wave sleep
active when no exogeneous stimuli
role in top-down responses to exogeneous stimuli

4. Brainstem maintenance of vigilance; arousal
Ascending pathways from pons/midbrain (RAF) → intralaminar nuclei of thalamus → forebrain
Control (with diencephalin nucleip) of wake/sleep cycle
Noradrenergic inputs from locus coeruleus → wakefulness + REM sleep
Cholinergic from pons → slow wave sleep
Receives sensory inputs (somatosensory, visual, & auditory especially → thalamo/1o cortices)
Orientation (forced attention) to sensory input
Saccadic eye movements (superior colliculus → frontal eye fields)

5. Attention - Definition
Presupposes vigilance
Ability to make choices for action among a myriad of competing stimuli in order to match task demands by
Enhancement of attended stimuli
Suppression of unattended stimuli
Requires executive skills (prioritize, etc.)
“ working memory
“ etc.

6. Control of attention
Exogenous (reflexive bottom-up – conscious awareness not required, imperative)
Endogenous (cortical, top-down choices to match on-going needs)
Monitor & maintain goal directed activities
Deactivate inappropriate tasks
Prepare activation of relevant tasks
Modulated by on-going affective signals (role of anterior cingulate cortex)

7. Bottom-up attention network
Selection of sensory saliency: (right) lateral intraparietal cortex – disengage from current target
Orient focus of attention: superior colliculus
Engage to new target, i.e., synchronize relevant cortical areas: pulvinar
[Enhance vigilance: RAF]
Posner 2012, Miller & Buschman 2013

8. Top-down attention network (goal-directed action)
Prefronto-parietal dorsal connectivity
Widespread cortical to subcortical areas
Lateral prefrontal - working memory, executive
Anterior cingulate - interface cognition & emotion
Diencephalic nuclei
Etc.
Multimodal intraparietal/temporo-parietal association cortical areas (right dominant > left)

9. Default mode network
Networks active/enhanced in the absence of exogeneous stimuli
Not “rest” but basis for continuous endogenous brain activity
Persists in sleep (except slow wave) and even under anesthesia
Associated with rapid (gamma, beta) EEG anteriorly, alpha (eyes closed) oscillations posteriorly

10. M. Raichle The restless brain Brain connectivity 2011; 1: 3-12
fMRI BOLD coherence in spatial networks activated by consecutive task evoked responses in a single subject

11. ADHD Bottom-up attention: spared
Default network: data presumed impaired
Top-down attention: multiply impaired, e.g.,
↓ response inhibition → impulsive
↓ sustained attention → distractible
↓ working memory → forgetful
↓ input inhibition and response monitoring
↓ awareness of affective signals & environmental rewards