Download Neural oscillations - Brain Dynamics Laboratory

20153486 Changju Lee
Visual System Neural Network Lab.
Department of Bio and Brain Engineering
Content
• Introduction
- Neural oscillation & Neural synchronization
- Schizophrenia (SCZ)
• Result
- Neural oscillation in SCZ
- Neurobiology of abnormal oscillations
- Neurodevelopmental hypothesis of SCZ
• Conclusion
Introduction – Neural oscillation
Global cortical
network
Local cortical
network
• Fundamental mechanism for enabling coordinated activity during
normal brain functioning
Introduction – Neural synchronization
• Correlations or coupling between spikes in two regions
Fell & Axmacher (2011), Nat. Rev. Neurosci.
• Neural oscillations and synchrony
Aperiodic signal
Quasi-periodic signal
Courtesy of D. Nikolić, Max-Planck Institute for Brain Research
Introduction – Schizophrenia (SCZ)
• Schizophrenia (SCZ)
: a mental disorder often characterized by abnormal social behavior and
failure to recognize what is real.
 Positive symptom : A range of psychotic symptoms
that most individuals do not normally experience.
e.g., sensory hallucination, delusion
 Negative symptom : an absence of behavior
e.g., poverty of speech, inability to experience
pleasure, lack of motivation
Self-portrait of Craig Finn
 Causes of SCZ are still unknown
 Distributed impairment involving many cortical areas and their connectivity
 Mechanisms that mediate the generation of coherent and coordinated activity in
cortical circuits will be the key understanding pathophysiology of SCZ
In this review article,
 Role of dysfunctional neural oscillations in SCZ with EEG and MEG
 Possible neurobiological causes of impaired oscillations of SCZ
 Neurodevelopmental hypothesis and oscillations of SCZ
Result – Neural oscillation in SCZ
Measuring neural oscillations in EEG and MEG signals
• Measurement of steady-state evoked potentials (SSEPs)
Steady-state
stimulation
SSEP
 Probe the ability of neuronal networks to generate and maintain oscillatory activity
• Measurement of evoked and induced oscillatory activity
 Evoked activity reflects bottom-up sensory transmission
 Induced oscillations represent the internal dynamics of
cortical networks
Courtesy of F. Roux, Max-Planck Institute for Brain Research
Result – Neural oscillation in SCZ
Neural oscillations and synchrony in SCZ
Kwon (1999), Arch. Gen. Psychiatry

Gallinat et al.(2004), Clin. Neurophysiol

Dysfunction in the auditory SSEP, in particular at 40 Hz.

Dysfunction in early sensory processes.
Dysfunctional phase synchrony during Gestalt
perception in SCZ.
 Impairments in neural oscillations are a
candidate mechanism for network in SCZ
Uhlhaas et al. (2006), J. Neurosci.
Result – Neurobiology of abnormal oscillations
Mechanisms underlying the generation of gamma oscillations and synchrony
Excitatory input
Mutual inhibition
Pyramidal
cells fire
Berlucchi (1972), Brain res.
repeat
Engel et al. (1991), Science.

Negative feedback inhibition of pyramidal cells by
GABAergic PV+ interneurons

Cortico-cortical connections mediate long-distance
synchronization with high precision
Result – Neurobiology of abnormal oscillations
Neurobiological correlates of deficits in neural oscillations and synchrony in SCZ
Anterior

Posterior
Rotarska-Jagiela et al. (2008), Neuroimage.
Changes in connectivity between healthy controls and
patients with SCZ according to Diffusion Tensor Imaging (DTI)

Lodge et al. (2009), J. Neurosci.
Hashimoto et al. (2003), J. Neurosci.

Ability of PV+ interneurons to express
important genes is impaired in SCZ
Reduction of PV+ neurons in the mPFC in an animal model of SCZ
Result – Neurodevelopmental hypothesis of SCZ
Emergence of high frequency oscillations and synchrony during the transition
from adolescence to adulthood

Gamma oscillations increase significantly during the
transition from adolescence to adulthood

Cortical networks reorganize during the transition from
adolescence to adulthood
Uhlhaas et al. (2009), Proc. Natl Acad. Sci. USA.
Hashimoto et al. (2009), Biol. Psychiatry.

Provide one mechanism for the late maturation of high
frequency oscillations in EEG data.

Predominance of GABA α2 subunit during early
development, whereas α1 subunit is expressed in adults
Conclusion
 Abnormalities in the synchronized oscillatory activity of neurons may have a central
role in the pathophysiology of SCZ
 PV+ interneurons generate gamma oscillation synchrony in local neural networks,
and corpus callosum transmits Interhemispheric information with high precision
 SCZ is characterized by abnormal brain maturation at several stages of
development, and typically manifests during late adolescence and early adulthood
Supplementary information
Fractional anisotropy