Two-way communication between the heart and the brain: Significance of time within the cardiac cycle

Abstract

Summarizes results of research dealing with time within the cardiac cycle as an experimental variable. In a variety of different experiments, meaningful sensorimotor events produced changes in heart rate that were systematically related to where in the cardiac cycle the events occurred. This function is proposed as a noninvasive measure in intact humans of cortically mediated effects on vagal control of the heart. Time within the cardiac cycle is also a dependent variable: Self-initiated responses are postponed to increasingly later times as momentary heart rate increases. It is hypothesized that this may result from visceral afferent feedback to the CNS via the baroreceptor nerves. Preliminary results are presented from acute cat experiments showing that changes in frequency of carotid sinus stimulation and differences in the direction of change affect the temporal pattern of discharge of the carotid sinus nerve. (19 ref)

Full text

Two-Way
Communication Between
the
Heart
and the
Brain
Significance
of
Time Within
the
Cardiac
Cycle
BEATRICE
C.
LACEY
Fels
Research
Institute
Wright
State
University
School
of
Medicine
JOHN
I.
LACEY
Pels
Research
Institute
Wright
State
University
School
oj
Medicine
ABSTRACT:
Results
oj
earlier
and
ongoing
research
dealing
with
time
within
the
cardiac cycle
as an ex-
perimental
variable
are
summarized.
In a
variety
oj
different
experiments,
meaningful
sensorimotor
events
produced
changes
in
heart
rate
that
were
systemati-
cally
related
to
where
in the
cardiac
cycle
the
events
occurred.
This
junction
is
proposed
as a
noninvasive
measure
in
intact
humans
oj
cortically
mediated
ejects
on
vagal
control
oj the
heart.
Time
within
the
cardiac
cycle
is
also
a
dependent
variable:
Self-initiated
re-
sponses
are
postponed
to
increasingly
later
times
as
momentary
heart
rate
increases.
It is
hypothesized
that
this
may
result
from
visceral
afferent
feedback
to
the
central
nervous
system
via the
baroreceptor
nerves.
Preliminary
results
are
presented
from
acute
cat ex-
periments
showing
that
changes
in
frequency
oj
carotid
sinus
stimulation,
and
differences
in the
direction
oj
change,
affect
the
temporal
pattern
of
discharge
of the
carotid
sinus
nerve.
Since
prehistoric times
it has
been known that
the
heart
has the
characteristic
of
autorhythmicity.
A
heart removed
from
the
chest
of a
slaughtered
animal,
or
from
the
chest
of a
human
in
prepara-
tion
for a
transplant, continues
to
beat
at its own
pace.
The
reason
is
that
the
origin
of the
heart-
beat lies within
the
heart itself.
In the
normal
heart,
the
beat
is
initiated
at the
sinoatrial node.
Here,
a
series
of
biochemical processes,
of
repeti-
tive membrane depolarization
and
repolarization,
results
in
repetitive transmission along
the
heart's
own
conductive tissue system, which,
in
turn,
re-
sults
in
cyclic contraction
and
relaxation
of the
cardiac muscle.
In
situ, within
the
chest cavity,
the
heart's
autorhythmicity
is
modified
by
both neural
and
humoral factors.
The
heart
is
slowed
and
speeded
by the
vagal
and
sympathetic cardiac
efferents.
But
action
at the
effector
organ does
not end the
process: Sensitive interoceptors
feed
back
to the
central nervous system
information
about
the
tim-
ing,
force,
volume,
and
pressure
of
each,
heartbeat.
This
feedback loop provides
an
oscillatory input
to the
central nervous system.
We
are
concerned
in
this article with limited
aspects
of the
significance
for
behavioral science
of
these
efferent
and
afferent
connections.
We
will
deal with
a
relatively novel variable: time within
the
cardiac cycle.
In our
studies
of
efferent
mech-
anisms
affecting
the
heart, time within
the
cardiac
cycle
is an
independent variable,
and we
discuss,
in
an
elementary way,
the
biochemical processes
at the
sinoatrial node.
In our
studies
of
presuma-
bly
afferent
mechanisms, time
is a
dependent vari-
able.
Our
presentation
is
limited
to
bare essentials,
since space does
not
permit
an
exposition
of the
statistical
and
experimental controls
we
employed
to
provide assurance
of the
validity
of our
general
statements.
Nor
have
we
time
to
discuss other
than main
effects.
On the
Efferent
Path
We
have spoken
in the
past
of the
"bradycardia
of
attention,"
for one
general
formulation
that
emerged
from
our
early work
was
that
the
inten-
tion
to
note
and
detect external stimuli results
in
This
article
was
presented
as a
Distinguished
Scientific
Contribution Award address
at the
meeting
of the
Ameri-
can
Psychological Association,
San
Francisco, August
1Q77.
The
research
was
supported
by
Grant
MH
623
from
the
National Institute
of
Mental Health.
Requests
for
reprints should
be
sent
to
either author,
Fels
Research Institute, Wright State University School
of
Medicine,
800
Livermore
Street, Yellow Springs, Ohio
45387.
AMERICAN PSYCHOLOGIST
•
FEBRUARY
1978
• 99
Copyright
1978
by the
American Psychological Association, Inc.
All
rights
of
reproduction
in any
form
reserved.