1. Neurophysiological Studies of
Auditory Verbal Hallucinations
Thomas Dierks
CAVEAT Fisher
Derek event related potentials) has a
Electrophysiology (EEG and EEG-based
long history in studies of schizophrenia Ford
Judy and serious mental illness.
Christoph Herrmann
Most were focused on establishing mental illness as a brain-based
Daniela Hubl
disease rather than a choice (c.f., Szasz, The Myth of Mental Illness).
They largely succeeded. Jochen Kindler
However, few were specifically focused on understanding the
Thomas Koenig
pathophysiology of specific symptoms.
Daniel Mathalon
I will be talking about those.
Kevin Spencer
Werner Strik
Ford JM, Dierks T, Fisher DJ, Herrmannvan Lutterveld et al.
Remko CS, Hubl D, Kindler J, Schizophr
Neurophysiological Studies of Auditory Verbal Hallucinations.
Bull. 2012.
Report from the International Consortium for Hallucination Research and Related Symptoms
Institute of Psychiatry, London, UK
September 13, 2011

2. I). Approachs to study auditory hallucinations
• A. Assessments of State
– Symptom Capture
• Periods of hallucinations and non-hallucinations are compared within
a patient
• These studies take two forms: passive studies and probe studies.
• B. Assessments of Trait
– Hallucinators vs. Non-hallucinators
• Hallucination severity is sometimes used in “individual differences”
studies.
• C. Mechanistic Studies of Trait
– Spontaneous neural activity model
– Inter-regional communication in the brain
– Self-monitoring failures

3. A. Assessments of State
Resting State Symptom Capture Studies
with Time-Frequency Analyses
As reviewed by Van Lutterveld et al 1, before the era of anti-psychotic
medications, depth electrocorticography studies were sometimes
conducted in conjunction with neurosurgery for relief of severe
psychotic symptoms. Other than providing an historical note, old EEG
findings are not easy to incorporate into the contemporary literature
with more sophisticated data collection and analysis.
Angelopoulos EEG 14 Increase in phase coupling in the alpha
band, both inter- and intra-hemispherically
between temporal and frontal lobes.
Highlights of traditional EEG/MEG analysis in symptom capture studies:
Little consistency regarding the frequency of the neural activity.
Good consistency regarding involvement of right and left auditory cortex, consistent with sMRI
and fMRI From Van Lutterveld et al, 2011.

4. A. Assessments of State
*Shortening of this microstate might indicate a
Resting State Symptom Capture Studies
premature termination of the delicate balance
Using ERPs/ERFs to External Probes
between goal-directed and salience-driven
processes, compatible with the observed
psychopathology.
*
•ERPs elicited by probes during an hallucination are smaller and later, suggesting
•the involvement of the auditory cortex in the generation of the hallucination.
•The line is busy.
From Van Lutterveld et al, 2011.

5. A. Assessments of State
Advantages and Disadvantages
• 1. Advantages
• Ability to observe neural activity preceding and during a
hallucinatory experience.
– Provides temporal and some spatial information.
– Nevertheless, few studies have used EEG in symptom capture.
• 2. Disadvantages
• The unknown contributions from shifting attention and motor
responses when the patient signals the beginning and ending
of a hallucination.
– Symptom capture studies require patience from the research
team and cooperation and insight from the patient.

6. B. Assessments of Trait
using Auditory Event-Related Potentials (ERPs)
• Comparing patients who do hallucinate to
patients who do not.
– It is typically not known, if the patients who do
hallucinate happen to be hallucinating during data
acquisition.
• Many of the studies that compare hallucinators
to non-hallucinators use event-related brain
potentials (ERPs) to auditory probes
– because they can reveal where and when in the brain
processing of auditory information is compromised by
the tendency to experience auditory verbal
hallucinations.

7. Auditory Event-Relatedcomponents
Where do the different Potential—ERP
come from and what do they reflect?
(a.k.a., evoked potential [EP], auditory evoked potential [AEP])
Middle latency responses: P3a and P3b:
Generator: Primary auditory cortex. Generators: Frontal and parietal lobes, respectively.
Function: They reflect early auditory Function: They reflect the allocation of
processing. attention, either elicited passively (orienting) or
effortfully.
MMN:
Generators: Secondary auditory
cortex and frontal lobes.
Function: It reflects automatic
registration of auditory sensory
memory.
N1:
Brain stem responses: Generators: Primary and
Generators: 8th nerve secondary auditory cortex, but
through brain stem is affected by frontal lobes.
Function: They reflect the Function: N1 reflects hearing From
integrity of the early levels and auditory SpringerImages.com, (Adapted
from Picton et al. 1974; Rissling
auditory system. perception. et al, 2010.)

8. What would it Event-Related Potential—ERP
Auditory mean if a particular component were
smaller (a.k.a., evoked potential [EP], auditory evoked potential [AEP])
in patients who were hallucinating?
Middle latency responses: P3a and P3b:
Generator: Primary auditory cortex. Generators:Voices are preventinglobes, respectively.
Frontal and parietal
Voices are disrupting processing of Function: They reflect the allocation of
Function: They reflect early auditory orienting or attending to
external auditory events in primary attention, either elicited passively or effortfully.
processing. external auditory
auditory cortex.
events, respectively.
MMN:
Generators: Secondary auditory
Voices are disrupting the
cortex and frontal lobes.
registration of auditory
Function: It reflects automatic
sensory memory.
registration of auditory sensory
memory.
N1:
Brain stem responses: Generators: Primary and
Generators: 8th nerve
Voices are disrupting secondary auditory cortex, but
Voices are disrupting processing
through brain external
processing of stem is affected by frontal events in
of external auditory lobes.
Function:events reflect the
auditory They in the brain Function: N1 reflects hearing
primary and secondary auditory From
integrity of the early
stem and perhaps thalamus. levels and auditory Hubl et
cortex (as shown by SpringerImages.com, (Adapted
from Picton et al. 1974; Rissling
auditory system. perception.
al., 2007). et al, 2010.)

9. Are these components are affected by the
Auditory Event-Related Potential—ERP
hallucinatory trait?
(a.k.a., evoked potential [EP], auditory evoked potential [AEP])
Middle latency responses: P3a and P3b:
Generator: Primary auditory cortex. Generators: that over 100 paperslobes,reported
Considering Frontal and parietal have respectively.
Derek Fisher’s lab has reported
Function: They reflect P1 and Function: They reflect the allocation of attention,
P300 reductions in schizophrenia, it is surprising that
relationships between early auditory
processing. severity across subjects. either elicited passivelyrelationship between P300
only 3 have reported a or effortfully.
hallucination
and AVH.
Recall the Caveat:
Failures to find relationships
between ERPs and the trait to
hallucinate could be due to a
failure to find a positive
MMN:
relationship or
UmbrichtGenerators: Secondary auditory
and Kjrles (2005) reported that
failure to test for such a
of the 22 cortex and frontal lobes.
MMN studies done in
relationship. schizophrenia, onlyIt reflectsrelationships
Function: 3 found automatic
between registration of auditory sensory
MMN and AVH.
memory.
Since then, Derek Fisher’s lab has
N1: reported small MMNs are related to AVH
Brain stem responses: Generators: Primary and severity.
th
Generators: 8reports of
There are no nerve secondaryno reports of N1 but
There are auditory cortex, Either the storage of auditory information
through brain stem being
brain stem responses is affected by frontal lobes.
being affected by the trait of in short term (echoic) memory or the
Function: They reflect the
affected by hallucination Function: N1 reflects hearing
hallucinations. registration that a deviant occurred, or
From
integritytrait. early
state or of the levels and auditory SpringerImages.com, (Adapted
both, is altered in patients whoal. 1974; Rissling
from Picton et have a
auditory system. perception. pre-disposition to hallucinate
et al, 2010.)

10. B. Assessments of Trait using ERPs to Probes
Advantages and Disadvantages
• 1. Advantages
• Comparing patients who do and do not hallucinate on MEG and EEG-based methods is far simpler
than comparing periods with hallucinations to periods with no hallucinations.
• The few successful studies using this method are consistent with the findings of the symptom
capture literature:
– Auditory cortex is “busy” in people who tend to hallucinate, interfering with processing auditory information
as early as 50ms (P1)after stimulus onset and as late as 200ms (MMN) and 300 ms (P300).
• Study by van Lutterveld and colleagues (2010) avoided a lot of these problems
2. Disadvantages
• Trait studies typically compare one group of patients who hallucinate to another group of patients
by usingnot.
who do healthy people who hallucinate.
Surprisingly, theyof an ERP component may be affected by larger P300s thanbut it will benon- by a
– The amplitude found that these people had the trait to hallucinate, healthy affected
lot of other individual differences that overwhelm the differences due to the tendency to hallucinate.
hallucinating subjects suggestingstudy the same persontypically seen symptomatic and once when
– To address this question, we need to P300 reduction twice, once when in schizophrenia
is not not. to the tendency to hallucinate.
due
• The preponderance of schizophrenia patients are medicated, and medication may decouple any
potential relationship between symptoms and neurobiology by attenuating symptoms, while not
affecting the ERP sensitivity to the propensity to experience those symptoms.
• We may be more successful at finding relationships with enduring features of the disease (the
diagnosis itself, or its subtypes) than with current symptoms.
• Other symptoms may combine with hallucinations to affect the neurobiology but not the severity of
the hallucinations.
• Some drugs of abuse might affect the neurobiology but not the current severity of the symptoms.
• Correlations between hallucinations and biology can only be as good as the assessment of
hallucinations.

11. C. Summary of Mechanistic Models and
Neurophysiological Findings
• Most symptom capture and trait studies using EEG and ERPs point to
involvement of left and right auditory cortex in AVH.
• PET and fMRI reveal more areas are involved than just auditory cortex!
• Remaining questions can be addressed with Mechanistic Models + fMRI data :
Why is auditory cortex busier in hallucinators and during hallucinations?
 Random noise increases sensitivity to weak signals through stochastic
resonance (Jaramillo & Wiesenfeld, 1998), and patients with
schizophrenia have “noisier” systems as indexed with EEG methods.
Why do thoughts become conscious and audible?
 Synchronized activity between key areas may promote conscious
perception of unbidden thoughts (EEG; Angelopoulos et al, 2011; Melloni
et al., 2007)
 Hyper-connectivity between auditory cortex and putamen makes
unbidden thoughts audible (fMRI data; Hoffman et al, 2011)
Why do AVH have negative content?
 Hyper-connectivity between amygdala and parahippocampal gyrus may
promote the sense of uncertainty and suspiciousness (fMRI; Bhatt et
al, 2012), and between putamen and auditory cortex may promote
audible thoughts (fMRI; Ford et al, in prep).
Why are percepts misperceived as coming from external sources?
 Self-monitoring deficits (EEG data; Ford et al., 2007)

12. Ideas for future research
• A. Combine EEG and fMRI methods
• Unexplored is the how specific baseline states affect the processing of
internal and external information that might serve as triggers for AVHs, or as
a trigger to interrupt such experiences.
• Such questions would require the combination of methods during symptom
capture to assess relationship between baseline state (spectral EEG, fMRI
measures of resting state connectivity) and ERPs to auditory probes
(c.f., Hubl et al 2007).
• B. More studies of mechanisms
• Self-monitoring mechanistic studies offer translation to bench neuroscience
and translation to other species, and hence open the door to invasive
manipulations that are not possible with in vivo human studies.
– For one example, studies like the ones reviewed above can be applied to
animals who make social calls, such as song-birds (Brainard and
Doupe, 2000) and non-human primates (Eliades and Wang, 2003).
– In such an experiment, perturbations of the neurotransmitters
implicated in schizophrenia might produce a pattern in the neural
signature of the mechanism that resembles the pattern seen in
schizophrenia patients who hallucinate.

13. Questions?
For a copy of the paper:
Judith.ford@ucsf.edu