ACTA NEUROBIOL. EXT. 1975, 35: 417429
Memorial Paper in Honor of Jerzy Konorski
KONORSKI'S CONCEPT OF GNOSTIC AREAS AND UNITS:
SOME ELECTROPHYSIOLOGICAL CONSIDERATIONS
E. Roy JOHN
Departments of Psychiatry and Physiology, New York Medical College
New York, N. Y., USA
One of the most enjoyable aspects of my long friendship with Jerzy
Konorski was that we viewed the problems of brain function from two
very different vantage points. Jerzy had accumulated a tremendous
volume of knowledge about the behavioral consequences of lesions of
different brain regions, much of which was derived from his own innumerable, ingenious experiments. My own work has consisted largely of
trying to infer the functional significance of observations of electrophysiological processes in different brain regions during behavior.
Whenever Jerzy's travels brought him to the United States and
whenever I found the opportunity to visit Warsaw, we resumed our
private debate. Our meetings were always the same: we greeted each
other with a warm hug, followed by inquiries about our family and mutual friends. Then Jerzy would rub his hands together briskly, his eyes
sparkling with anticipation, and say: 'Well, tell me what's new'. Hours
of joyous altercation then ensued, as we tried to reconcile our different
data bases. Sometimes we ate during these discussions, but I doubt that
Jerzy would have noticed if the plates had dissolved, he was so intent
on the problem.
He was obsessed with the need to understand. I have seldom known
a man who pursued knowledge with such brilliance, energy and lustiness.
His death was all the more a shock because he was intellectually such
a vigorous and youthful person.
I found it characteristic, in these discussions, that Jerzy never chose
the easy solution of dismissing as of questionable functional relevance
any electrophysiological findings which contradicted his expectations.
Rather, he persisted in seeking ways to reconcile such findings with
418
E. R. JOHN
the more familiar results of his lesion studies, accepting the aggravating
reality that the same central nervous system could generate two apparently contradictory kinds of evidence. It seems particularly appropriate
to follow his lead in this regard in selecting the topic for a contribution
to his memorial volume.
The concept of gnostic areas and units
In his monumental work, Integrative Activity of the Brain, Jerzy
used psychological data and neurological observations to survey the
main categories of unitary perceptions. By unitary perceptions he meant
those stimulus-objects recognizable by a single non-analytic process,
in contrast with complex perceptions requiring resolution into constituent elements for recognition to occur. Among the principles and characteristics of unitary perceptions which he listed was the important feature
that neurological evidence clearly shows that limited cortical lesions are
capable of abolishing particular categories of perceptions, leaving other
categories of the same afferent system practically unaffected. He constructed an exhaustive catalogue of the perceptual deficits correlated
with local cortical lesions in man. He argued that every category of
perception was mediated by a specific portion of the associative areas
of the cortex. The region of cortex subserving a particular class of perceptions was called a gnostic area or gnostic field. Individual neurons
in afferent fields were envisaged as encoding sensory elements pertaining
to a stimulus into more and more complex patterns. As the information
about disparate features of the stimulus object converge upon successively higher levels, these separate features no longer participate as separate items in further information processing, but become indissolubly
amalgamated into a percept of the whole. Thus, Jerzy assumed that a t
a sufficiently high level within analyzer systems, unitary perceptions
are mediated by the discharge of single neurons, called gnostic units.
Gnostic areas were considered as files of gnostic units representing all
of the unitary perceptions established in a given subject. Jerzy envisaged
redundant representation of each unitary perception by a number of
gnostic units, constituting a set of gnostic units all representing the same
stimulus features.
Finally, he proposed that once a potential gnostic unit had been
preempted by a particular stimulus pattern so as to become transformed
into an actual gnostic unit representing that unitary perception, it became
resistant to any new stimulus pattern. In other words, a gnostic unit
could only participate in representation of a single unitary perception.
Representation of a new pattern requires establishment of a new gnostic
unit or set of units. Establishment of a gnostic unit mediating a particul-
KONORSKI'S CONCEPT OF GNOSTIC UNITS
419
a r perception involves an increase in the transmissibility (facilitation)
of synapses, transforming them from potential to actual connections.
Jerzy assumed that activity of gnostic units corresponds to biologically meaningful stimulus patterns used in associative processes. By
careful analysis of the covariation between different sensory dimensions
or modalities of perceptual deficits after local lesions, he derived diagrams of the associations between different gnostic fields. These associations were interpreted as evidence that anatomical pathways connected
the corresponding cortical regions.
Jerzy pointed out (p. 76) that there was, at the time he wrote, no
direct electrophysiological evidence that perceptions were really represented by units in gnostic areas. He based his conclusions on indirect
evidence from psychological considerations, neuroanatomical and neuropathological findings, and effects of brain stimulation in waking human
subjects. In this paper I will present some of our current electrophysiological studies relevant to the question of whether gnostic areas and
gnostic units exist.
Do gnostic areas exist?
Jacobo Grinberg-Zylberbaum and I recently carried out an electrophysiological experiment on human subjects which yielded results bearing upon the question of the existence of gnostic areas (unpublished
observations). The experiment consisted of two portions. In the first
part, subjects seated before a tachistoscope viewed brief presentations
of a vertical line, followed by presentation of the number '2'. This stimulus sequence was repeated 50 times at intervals of 1 sec, while evoked
responses to the vertical line were recorded from occipital (01and O,),
parietal (P3,
P4 and P,), and temporal (T, and T6) derivations using
a linked earlobe reference 1. The subject then viewed 50 presentations
of the same vertical line, but now followed by the letter 'J'. Evoked
responses to the vertical line were again recorded during this second
stimulus sequence.
During the first sequence, in which the vertical line was followed
by the number '2', it was perceived as the number '1'. During the second
sequence, when the vertical line was followed by the letter 'J', it u.as
perceived as the letter '1'. Thus, the same vertical line activated two
different unitary perceptions, which should be represented by different
gnostic units in the gnostic field for visual signs (V-SN). It is noteworthy
that Jerzy located gnostic visual fields further lateral and rostra1 than
areas 18 and 19. He reasoned that they probably encroached upon tem1
2
Derivation labels refer to positions in the International
- Acta Neurobiologiae
Experimentalis
lo/,,
Electrode System.
420
E. R. JOHN
poral cortex (areas 37 and 22) and parietal cortex (area 39 and posterior
part of area 7). In particular, he suggested that the gnostic field for visual signs (V-SN) was probably located in the dominant hemisphere
around area 7B (p. 123). This locus would lie between electrode P, and P,
in the 10120 system.
Using a PDP 12 computer, average evoked responses (AER) and
standard deviations were computed from each derivation, for the vertical line in the two different sequences. The AER to the vertical line perceived as a number was then substracted from the AER to the vertical
line perceived as a letter. The significance of the resulting difference
wave was assessed at many points along the wave, each representing
successive latency increments of 2 msec, by use of the t-test. The results
from two typical subjects are illustrated in Fig. 1.
Figure 1 shows that no significant differences were found between
the AERs to the vertical line under the two different perceptual sets
and 0,). That is, the sensation
in the primary visual receiving areas (01
caused by the vertical line was essentially the same in both stimulus
sequences. However, significant differences did occur in the parietal
and temporal derivation, presumably related to the two different perceptions. Essentially the same procedure was used by Johnston and Chesney
(1974), who obtained results comparable to ours. Differences between
the two perceptual sets were found in frontal but not occipital regions.
No data were obtained from parietal or temporal derivations in that
study.
In the second experiment, a four stimulus sequence was tachistoscopically presented, consisting of a large A, a small a, a large E, and
a small e. This sequence was repeated 50 times. AERs and standard
deviations were again computed for the response to each stimulus from
every derivation. The results are shown in Fig. 2.
When the AER's elicited by small and large versions of the same
letter were compared, significant differences were found in the occipital
derivations. That is, large and small letters produce different sensations.
However, no significant differences were found in temporal or parietal
derivations. Large and small versions of the same letter activate t h e
same perception, denoting a particular symbol in the alphabet. Finally,
when AER's elicited by A's and E's of the same size were compared,
significant differences were found in all derivations. Both the sensations
and the perceptions elicited by two different letters a r e different.
What does this experiment tell us about gnostic fields? First of all,
it confirms Jerzy's expectation of qualitatively different processes in
primary sensory projection areas and association areas. Second, the
electrophysiological reflection of the unitary perception of letters and
KONORSKI'S CONCEPT 01;' GNOSTIC UNITS
" I"AS A NUMBER VS ' 1'' AS A LETTER
i AS A NUMBER
DIFFERENCE WAVE
""
w
w v c--1
t TEST
S. J.
S.J.
1 AS A NUMBER
0.0:LEVEL+[
,
.*- --,
L .'::.!
S. J.
w - p
5;
%L\c?~
L .T
J.C.
L.T.
Fig. 1. Top: Examples of averaged evoked potentials to a vertical line presented
in a context of numbers (line 1) and in a context of letters (line 2). The difference
wave obtained by subtracting line 2 from line 1 is shown in line 3. Line 4 shows
the value of the t-test at each point along this analysis epoch. Statistical significant
differences were obtained in parietal and temporal derivations in the evoked potential components located between 150 and 200 msec of latency. Each average
evoked potential was computed from 100 samples. Average responses, variances,
difference waves and the t-test were computed using a PDP-12 computer.
Bottom: Same data from a second subject.
4.522
E. R. JOHN
Fig. 2. Top: The difference wave (line 1 ) and the t-test (line 2) obtained by comparing average evoked potentials (100 samples) elicited by a big "A" and a little
'caw . Only the occipital location shows a statistically significant difference.
Bottom: The same calculations, but now between evoked potentials elicited by
a capital "A" and a capital "Em.All the locations show highly significant differences
between, these evoked potentials.
KONORSKI'S CONCEPT OF GNOSTIC UNITS
423
numbers was found much more extensively than he predicted. Instead
of being restricted to gnostic field V-SN, corresponding to the parietal
regions, marked differences were also found in temporal and frontal
regions. How can this be reconciled with the selective deficit called
alexic agnosia, caused by lesions in this gnostic field, as illustrated in
the six cases of Alajouanine et al. to which Jerzy referred?
One possibility is that the electrophysiological processes manifested
in these various anatomical regions are not correlated with the neuronal
processes underlying the perception of the stimuli which are responsible
for the electrophysiological responses. They may not be relevant to
such functions as unitary perception. While this possibility must be
recognized, it is nonetheless evident that markedly different neuronal
processes are released in temporal and frontal as well as parietal regions
when a vertical line is perceived as a letter or as a number, and these
different neuronal processes are manifested by different electrophysiological signs. Unless we prefer to prejudge the issue, we cannot assume
that these processes are not functionally relevant just because alexic
agnosia is not produced by temporal or frontal lesions.
Jerzy's inclination at this point, I believe, would have been to ask
two questions: what is the significance of the appearance of these electrophysiological signs in more extensive regions than only the parietal,
and why does alexic agnosia only result from damage in gnostic field
V-SN?
First of all, I am not sufficiently well informed to know whether
damage to temporal or frontal cortex can also produce alexic agnosia
or whether damage to gnostic field V-SN invariably produces alexic
agnosia. A thorough survey of the neurological literature would be necessary to answer those questions. If damage to temporal or frontal
cortex sometimes produces alexic agnosia or even causes increased frequency of errors in the interpretation of visual signs, or if correct interpretation of visual signs ever survives destruction of gnostic field V-SN,
then we would have evidence that these functions are not exclusively
localized within that cortical region.
However, in the absence of such information let us assume that no
such evidence exists. Would this mean that the observed activity in temporal and frontal regions was functionally irrelevant and that gnostic
units for letters of the alphabet only existed in field V-SN?
In our studies of neural readout from memory in cats (John et al.
1973), we showed that the AER contained exogenous processes, related
to the afferent input of information about stimuli (sensation) and endogenous processes related to the interpretation of the meaning of that
424
E. R. JOHN
incoming information (perception and cognition). In later work (Bartlett
and John 1973), we showed that these processes were separable and
described computer methods to quantify the contribution of exogenous
and endogenous processes to the electrophysiological activity of any brain
region.
Application of these methods to data obtained from many different
brain regions in a large sample of cats performing differential generalization to visual or auditory signals produced the results shown in Fig. 3.
Fig. 3. Plot of mean correlation coefficients
between exogenous residuals vs. endogenous
FLICKER
residuals for different neural systems and
CLICKER 0
for different cue modalities.
Closed circles: Flicker frequencies as stimuli.
a
Auditory system: N = 305 (N - number of
independent measurements); Aud. Cx. (16
cats), Med. Genic. (16), Brach. Inf. Coll. (1).
Limbic system: N = 303; Hippocampus (16),
Dentate (5), Cingulate (51, Septum (5), Prepyriform (6), ~Med. Forebrain Bundle (61,
Mamm. Bodies (5), Hypothalamus (7). Mesencephalic non-specific: N = 158; Retic. Form.
(IS), Cent. Gray (I), Cent. Teg. Tract (1).
Motor system: N = 146; Motor Cx. (4), Subs.
Nigra (lo), Nuc. Ruber (4), Nuc. Vent. (91,
SYSTEM
z 06
Subthal. (5). Other sensory: N = 54; SensoriW
= 05.
motor Cx. (4), Nuc. Post. Lat. (I), Nuc. Vent.
Post. Lat. (5), Nuc. Vent. Post. Med. (1). Tha04
lamic non-specific: N = 139; Cent. Lat. (13),
00
10 20 30 40 50 60
Retic. (6)'
(l)' Med'
MEAN CORRELATION BETWEEN EXOGENOUS RESIDUALS
(5), Pulvinar (1).
Visual system: N = 394, Visual Cx (IS), Lat. Genic. (IS), Sup. Coll. (2).
Open circles: Click frequencies as stimuli. Auditory system: N = 48; Aud. Cx. (5
cats), Med. Genic (5). Limbic system: N = 69; Hippocampus (5), Dentate (31, Cingulate (3), Septum (31, Prepyriform (2), Med. Forebrain Bundle (31, Mamm. Bodies
(3), Hypothalamus (2). Motor system: N -- 37; Motor Cx. (I), Subs. Nigra (41, Nuc.
Ruber (I), Nuc. Vent. Ant. (5), Subthal. (2). Non-specific system: N = 50, Mesen.
Retic. Form. (6), Cent. Gray (I), Cent. Teg. Tract (I), Cent. Lat. (3), Nuc. Retic. (3).
Visual system: N = 55; Visual Cx. (6), Lat. Genic. (6), Sup. Coll. (1).
Data from monopolar and bipolar derivations were combined. Replications varied
across cats and structures (Data from Bartlett et al. 1975).
40
V)
O
The presence of information about the signal could be demonstrated in
all of those various regions, but with a great quantitative difference in
the signal-to-noise ratio, as reflected in the rank order of structures
along the horizontal (exogenous) axis. The presence of activity related
to the interpretation of that information could also be demonstrated in
all of those brain regions. An even greater quantitative difference among
KONORSKI'S CONCEPT OF GNOSTIC UNITS
425
various structures existed in the signal-to-noise ratio for this type of
activity, as seen from the logarithmic scale of the vertical (endogenous)
axis, although approximately the same rank order was preserved.
These data indicate that the endogenous processes reflecting particula r perceptual and cognitive functions have a very widespread distribution. The fact that the values found for these processes span a range
of 1,000 indicates great quantitative differences between anatomical
regions in the density or intensity of representation of gnostic function.
Perhaps, under normal circumstances, the brain of an individual requires
some threshold value for the signal-to-noise ratio to be exceeded in order
for information represented by the corresponding neural activity to be
functionally useful. If that threshold value is only surpassed by one particular brain region, damage to that region and to no other region will
produce impairment of that function. Nonetheless, the relevant information is available in many other places. Perhaps, if the threshold value
for the siglnal-to-noise ratio could be lowered, restoration of the impaired function might be achieved even though irreversible damage had been
sustained by the region which previously achieved the highest signal-to-noise ratio.
This reasoning seems particularly plausible if we consider that the
greater informational reliability of a high signal-to-noise ratio, as life
experiences accumulated, would tend to establish functional dependence
upon the region displaying the highest signal-to-noise ratio and a learned
threshold setting which would reject information from regions with
a lower signal-to-noise ratio. Thus, a learned functional inhibition might
even be established which prevented such alternate regions from resuming functional utility in the event that the region usually mediating
that function were damaged.
These speculations offer a way to reconcile Jerzy's conclusions and
the observations upon which they were based with the apparently contradictory electrophysiological findings in our studies. Perhaps the signal-to-noise ratios for activity related to the perception of letters and
numbers is highest i n V-SN, and the threshold in the normal brain is
usually set to reject lower signal-to-noise ratios for that activity. Such
lower signal-to-noise ratios might exist in temporal or frontal regions.
Thus, although information relevant to the perception of letters and
numbers is available in those regions, damage there will not result in
alexic agnosia nor can they sustain such perception alone if gnostic field
V-SN is damaged. While 1 have no evidence at present that these speculations are correct, they provide an attractive working hypothesis. Attractive not only because thus no contradiction need exist between two
bodies of data, both of which reflect real aspects of brain function, but
426
E. R. JOHN
also because were this hypothesis correct much functional deficit due
to brain damage which we presently consider irreversible might eventually prove to respond to treatments which lower the relevant thresholds or block the learned functional inhibitions.
Do gnostic units exist?
I want now to turn to the second question addressed by this paper:
to gnostic units exist? Let us recall that Jerzy assumed that gnostic
units were neurons which were transformed by a process of synaptic
facilitation so that silbsequently they responded only when the corresponding unitary perception occurred. Further, these gnostic units were
resistant to future changes, specifically excluded from participation in
multiple perceptions by certain aspects of Jerzy's theoretical argument.
Several kinds of evidence seem to controvert Jerzy's expectations.
In another article (John 1972), I reviewed much of the data which opposes the conclusion that a process of synaptic facilitation recruits neurons to the representation of perceptual experiences. Among the findings
cited in that article were numerous reports that changes in neuronal
response during learning only occur in polysensory units which respond
to all of the associated stimuli before the learning experience. Since
Jerzy presented compelling arguments that gnostic units must be initially uncommitted and come to represent unitary percepts as the result
of experiences, such findings cannot be reconciled with his contention
that gnostic units become committed by the transformation of potential
to actual connections.
In the same article, I reviewed the evidence that a high proportion
of units, ranging from 10°/o to 60°/o in various studies, change their
response even in simple learning tasks. Given the high probability of
modification of unit activity with experience which is apparent from
these reports, it seems very unlikely that a gnostic unit, once committed,
could be 'immunized' or protected against subsequent involvement in
the mediation of new perceptions, as required by Jerzy's formulation.
Finally, for five years my colleagues and I have been studying unit
behavior in discrimination learning (John and Morgades 1969abc, Ramos and Schwartz 1974, Ramos et al. 1974ab, John 1974). In those studies
we have utilized chronically implanted, movable microelectrodes to examine the responses of small groups of neurons and, more recently,
well-isolated single neurons, during correct responses and errors in tasks
requiring differentiated behavioral responses to discriminated visual
stimuli, and also during differential generalization to ambiguous stimuli
delivered to differentially trained animals.
KONORSKI'S CONCEPT O F GNOSTIC UNITS
42 7
Evoked potentials and unit responses were simultaneously recorded
from both cortical and subcortical microelectrodes in these cats. Cortical
electrodes were located both in specific projection and association areas.
Using computer pattern recognition techniques described elsewhere in
detail (Barlett, John, Shimokochi and Kleinrnan 1975), single evoked
potentials from trials resulting in correct vs. erroneous performance to
the same conditioned stimulus or from differential generalization trials
in which two different behaviors were elicited by the same novel test
stimulus were classified. This classification procedure identified the evoked potentials as belonging to one or another of the 'readout modes'
which reflected the activation of memories about different stimulus-response contingencies. Particular readout modes were found to be differentially correlated, at extremely high significance levels, with the subsequent behavioral performance. Therefore, occurrence of a particular
readout mode can be interpreted as evidence that the stimulus eliciting
that electrophysiological and behavioral response was perceived as a signal with a particular significance.
When the pattern recognition procedure had identified the readout
mode activated by each stimulus in the behavioral trial, the firing patterns of the simultaneously recorded unit activity corresponding to each
readout mode were separately analyzed. We found two types of neurons
in these analyses. One type showed an invariant average pattern of response to a given stimulus, no matter how it was perceived (i.e., no matter what behavioral response ensued). These units might be described as
'stimulus-bound', responding to the signal in the same way independent
of perception. The second type of neuron showed one average temporal
pattern of response during one readout mode and a different average
temporal pattern of response during another readout mode. These units
might be described as 'gnostic' units, with a response pattern related
to the perception rather than determined by the sensation. Such units
showed great variability in their responses during a specified readout
mode, but displayed a characteristic and specific average response in
each mode. Different units of this type in the same anatomical region
showed closely similar average responses during the same mode, although
their responses to single stimuli were poorly synchronized. These findings suggested an 'ergodic' hypothesis, that is, the average response
across the set of units of th.is type to a sing7e stimulus presentation eliciting a specified readout mode corresponded to the average response of
any unit of this type to a set of stimulus presentationseliciting that
specific readout mode. In view of these data, it would seem that the perception of a stimulus is mediated by the averaged temporal firing pattern of an ensemble or set of units of this type. The activity of any sin-
428
E. R . JOHN
gle unit is important only insofar as it contributes to the statistical behavior of the ensemble.
Further, firing of any unit per se seems to have no unique informational value. All units thus far observed not only fire 'spontaneously'
and show great variability in response to any stimulus, but show a differential response consisting of differences in graded temporal patterns,
rather than the all-or-none behavior postulated in Jerzy's theory.
As yet, we have not observed a single neuron which fired only during one readout mode and not in another, or which displayed patterned
discharge in m e mode and random activity in all other modes. Thus, we
have so far failed to observe any neuron with the characteristics of the
gnostic units which Jerzy postulated.
In spite of this apparent failure to confirm Jerzy's predictions, I must
hasten to point out that even after years of study we have succeeded in
analyzing only a small number of units and most of those have not been
in associative cortex.
It may well be that further studies, especially studies conducted in
other cortical regions more relevant to the peculiar stimulus dimensions
critical for the discriminations required in our behavioral tasks, will reveal the existence of gnostic units with the predicted features. We are
continuing to pursue these studies in the hope that we will either find
such units or amass a sufficient volume of data to justify rejection of
the hypothesis.
I deeply regret that Jerzy Konorski is no longer alive to discuss these
findings, to guide us with his intuition and vast knowledge, and to inspire us with his unlimited enthusiasm for the quest after understanding.
When the answer to these intriguing problems finally becomes clear,
whether Jerzy's hypotheses were right or wrong, I am sure that his
contributions will have been invaluable. He was a rare one and I miss
him.
This work was supported in part by Grant No. MH 20059 from the National
Institute of Mental Health.
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KONORSKI'S CONCEPT O F GNOSTIC UNITS
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E. Roy JOHN, Brain Research Laboratories, New York Medical College, New York, New
York 10029, USA.