Professor für Neurobiophysik im Ruhestand
Vorlesung jeweils im Wintersemester
über das Gehirn und das Bewusstsein. Das Bewusstsein läßt sich zwar nicht in die Naturwissenschaft integrieren,
aber man kann die Inhalte des phänomenalen Niveaus des Bewusstseins beschreiben und mit Kenntnissen aus
der Neurowissenschaft vergleichen. Besondere Bedeutung kommt der Zeitachse zu.
Näheres (Zeit und Ort) gebe ich jeweils in http://www.brain-kruger.de bekannt.
Mirror neurones, in collaboration with Dip. Neuroscienze, Università degli Studi, Parma
2. Magneto-akustische Reizung des Nervensystems
Magneto-acoustic stimulation of the nervous system,
in collaboration with Neurologische Universitätsklinik, Freiburg
3. Schizophrenie und Affen
Schizophrenia and monkeys
4. Physik und die phänomenalen Gehalte des Bewusstseins, cf. http://www.brain-kruger.de
Physics and the phenomenal contents of consciousness.
5. Frühere Arbeiten
6. Arbeitsweise des Ruheständlers.
Mode of work of the retired scientist.
1. Mirror neurones
were done with 64 chronically implanted microelectrodes from the monkey
"mirror neurone area" F5 in the ventral premotor cortex. The monkey was
given food by hand, and also with a pliers which the animal never had
seen before. We could show that the multineuronal
excitation pattern elicited by viewing the pliers became very similar
to the one evoked by the hand after three trials only. In
contrast, a device operating with a thread and a tube, also
delivering food to the monkey, but looking and functioning very
differently as compared to the hand and the pliers, never evoked excitation
patterns similar to those of the hand. Work done with R. Dalla Volta
and F. Grammont.
With F. Caruana and G. Rizzolatti (Dip. Neuroscienze, Università degli Studi, Parma) it will be attempted to confirm this observation on
another monkey, using a greater variety of food-delivering instruments.
A more detailed report will soon be available here.
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2. Magneto-acoustic stimulation.
It is attempted to stimulate nervous tissue with a combination of
ultrasound and a magnetic field oscillating at the same frequency. The
basic idea is that the tissue moves in the instantaneous magnetic
field, with the movement and the magnetic field directions inverting at
the same instant so that the induced voltage continues to head in the
same direction during many oscillation periods. With respect to
focalisation and intensity we expect advantages over Transcranial
Magnetic Stimulation and mere ultrasound stimulation. A 6 kW-generator
of oscillating magnetic fields and an adequate ultrasound generator is
now available. We currently explore
the conditions of testing the desired effects in nervous tissues of
different kinds. Work done with Neurologische Universitätsklinik, Freiburg and H. Kaube, München.
A more detailed report will soon be available here.
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3. Schizophrenia and monkeys
An evolutionary consideration about schizophrenia in monkeys.
A monkey model for human schizophrenia would be extremely valuable but
it appears that there is no such model in a convincing way. This text
concerns the possibility to study a derangement in monkeys which may be
related to human schizophrenia, and thereby to offer a new gate to find
a specific therapy. The likelihood of success may be small but the
severity, the frequency, and the duration of the disease makes it
worthwile to consider the present view.
Among neuroscientists there is a wide consensus about the differences
between monkey and man: monkeys are "humans minus language" while the
remaining faculties are present to a reduced extent. Other views will
be discussed elsewhere.
The present view rests on a more specific statement on ".. minus language":
The biological construction principle of the head is remarkably stable
from fish (or even insect) to frog to bird to rat. One may conclude
that there is a particularly high obstacle on the way to possible
alternatives. Here the relevant feature is that the principal effector,
not for locomotion but for "mani"pulations, i. e. the mouth or the
beak, is rigidly coupled to the eyes. In cases of visually guided
actions, the animal has to take care only of two
relevant positions: that of the object acted upon, and that of the eyes
which in turn have some rigid neuronal coupling to the effector
Monkeys with huge brains have introduced the use of hands. The consequence is that they have to take into account three
positions, namely those of the object, of the hand and of the eyes.
Instead of the above rigid coupling they have evolved a powerful
control machinery for visually guided manipulations.
One can learn from robot engineers who build video-guided grasping
tools that the introduction of a foreign, similarly looking tool into
the visual field of the camera will lead to a severe perturbation of
the control circuitry. This is the "new problem" introduced by the
evolutionary step towards monkeys. They had to evolve a supplementary
control which is: "Sensorily controlled manipulations must be based on
sensory impressions of own
hands. Block the hand motor output if signals from foreign hands are
recognised". Or stated otherwise: "Don't attempt to base motor commands
on pertinent sensory impressions that are, in some sense, fictive." No
such rule was necessary in other animals.
Another stream of cerebral evolution went towards increasingly complex
and long-lasting non-repetititve procedures. ("Procedures" are "bicycle
riding", or "eating with a spoon", or "building a nest". ) The longer
they last, the more likely is an interruption. The usual way of
restarting an interrupted procedure is to rely on the sensory
recognition of one's own partial achievements: the rabbit need not
recall how far it has dug its burrow. Rather, the half-dug burrow
serves for a kind of external memory. Obviously, the drawback is that
the relevant structures must remain constant during the pause.
Typically this is not true if the results of a procedure are sent away,
or otherwise are withdrawn from continued observation shortly after the
moment of production, and the procedure does not allow a restart. A
case in point is a prolonged medical treatment of a patient: it is
impossible to found the next step of the treatment exclusively on
actual observations of the patient, without taking into account which
pills have already been given.
The limitation can be overcome by constructing a type of memory
("episodic") that stores the essential sensory features at the instant
of interruption, and later reproduces them.
The present view is that this step alone characterises the transition from monkeys to humans.
However, the step is extremely dangerous: it implies that one generates
a fictive sensory impression at another than the original instant.
Progress towards humans brings about this "new problem". I do not
believe that any animal species other than humans has ever done this
step. The excellent memory of monkeys and apes most probably is
of the type "procedural"; one cannot prove that it is "episodic". The
manifestation of fictiveness resides in the fact that this type of
apparent sensory impression may not, or must not be altered by motor
commands: one cannot change, by present own motor acts, the contents of
a recalled sensory scene.
The particular point of the present text is this: The evolution towards
humans would not have taken place if monkeys had not existed before,
and if they had not prepared the way how to cope with "fictive" sensory
impressions, although the view of a foreign hand is "fictive" in a much
narrower sense than the view-like recall of my past hand, or any other
past scene. The common aspect, in both cases, is "Don't attempt
to base behavioural output on pertinent sensory impressions that are,
in some sense, fictive".
As soon as the safe operation of the rule was established,
monkeys could even turn the new situation into an advantage unrelated
to sensorimotor control ("mirror neurones") allowing them to draw some
conclusions about motor acts of conspecifics. With the advent of
episodic memory, humans, too, could go beyond a mere interruption
management, and begin to draw conclusions from past to future. Both
monkey and man had to fuse the fictive signals with some real ones in
an intricate way. In that fusion process the real signals have to
dominate, i.e., in the case of hands, those originating from my hand (for monkeys), or my present
hand (for humans). Only if this fusion is achieved appropriately, a
motor behaviour can be generated. In the example of a medical treatment
given above, it is not sufficient that the doctor generates a
quasi-sensory impression ("recall") of the last step of the treatment,
but he/she has also to make sure that the patient, and the pills for
the next treatment, exist at present. With respect to the timing of
motor output, the latter "real" components must have absolute priority.
This sounds trivial but such complications do not occur in a rat.
A peculiar example is human speech. The physical effects of speech are
sent away so that an interrupted stream of speech (as it occurs in
every dialog) could not be continued without the abovementioned
interruption management. Monkeys cannot speak in a human sense because
they lack that management. They can only use what in humans would
correspond to the grammatical category of imperatives, whose simpler
forms can run without that management. (A facial expression is an
imperative.) Thus, the absence of speech is not a deficit of
communication proper, but it is a lack of an evolutionary step within
each individual monkey. This is meant by "... minus language".
It does not come as a surprise that the human Broca area has indeed
been found to be homolog, or an extension, of the monkey mirror neurone
area F5 in the ventral premotor cortex. In my opinion, the reason is
not that human language evolved from manual gestures but rather that
this region is the site of the proper treatment of fictive signals in
the sense as explained above. To say it once more: in the present
context "reality" means to receive correlating sensory feedback from
own motor commands, and "fiction" means to have sensorily comparable
situations where own motor commands have no such effect.
The obvious relationships to consciousness cannot be discussed here.
A cerebral derangement that leads to a confusion of real and fictive
situations might be the most general way of describing schizophrenia.
If a patient hears non-existing voices, then this can only be based,
perhaps indirectly, on a retrieval from some memory of an episodic type.
The purpose of the present text is to point out that a similar
physiological disease in monkeys and humans, attaining the way how
"fiction", in the present sense, is treated, would have different
effects in these two species. It would be a derangement that is related
to the way how sensory-like signals from past experiences (in humans),
and sensory signals from foreign individuals (in monkeys),
respectively, are brought together with own present sensory signals, in
order to merge them into a reasonable behavioural output.
The disease is the price to be paid in evolution for becoming a monkey, and a human, respectively.
The conclusion is that one would have to look, in monkeys, for
inappropriate behavioural signs of the treatment of sensory signals
coming from other monkeys or humans ("monkey schizophrenia"). However,
the ubiquitous social signals exchanged within all animal species must
be excluded. (Each rat or each insect has to recognise its conspecifics
but it cannot, and need not "know" that itself it is such a
conspecific, too.) Rather, one would have to focus on signals that can
originate from another individual as well as from the animal itself,
just as in the case of viewing a hand. If one can find a means to damp
or, on the other hand, to provoke such signs in monkeys, then there is
a certain chance that these means are similarly effective also for
If the rate of occurrence of monkey and human schizophrenia is
comparable, then some casual observations must already have been made
in the numerous scientific institutes, monkey elevation stations, or
zoological gardens. It would be a first step to collect such reports,
in order to delimit typical or frequent cases. The outcome of that step
may lay a better foundation for a more powerful attack. At this point,
schizophrenia experts must guide the investigations.
At present there is a monkey at the Dip. Neuroscienze in Parma that
apparently has no genuinely visual defect but that is unable to guide
his hand appropriately when it has to execute different varieties of
grasping. Instead of adjusting the type of grasp to the actual
situation, the animal tends to use the same grasp as the previous one
even if it is now inappropriate, and thus to deprive itself from
receiving a reward. So far, the animal has not been examined for more
pertinent defects. I do not mention this case because I am convinced
that it is particularly relevant. Rather, it is an example for a case
in which no one would have thought of an even remote link to
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4. Physics and the phenomenal contents of consciousness.
See the website http://www.brain-kruger.de.
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5. Previous work
(done with various collaborators, and guided by various directors)
Proton magnetic resonance at low magnetic fields. Resonance in a
rotating frame of reference (Failure of finding some non-trivial effect
under this condition). Resonance in a magnetic field gradient (Rescue
program foreseen for the case of failure of the previous project).
Multiple-quantum transitions. Until 1965; Diploma thesis, physics,
Attempt to visualise the dynamic spatial distribution
of normal/supraconducting domains in supraconductors type 2, using a
reflection electron microscope. Failure for reasons of organisation.
Until 1969; CNRS-Basses Températures, Grenoble.
Thermal properties of demixing glasses at low temperatures. Until 1971; Doctoral thesis. CNRS-Basses Températures, Grenoble.
Demonstration of vigorous discharges in cat retinal ganglion cells elicited by
far peripheral stimuli ("periphery effect", later "shift effect").
(1972-1979) Neurologische Universitätsklinik, Freiburg
Colour processing in visual cortical areas of the monkey (1975-1977) Neurologische Universitätsklinik, Freiburg
Recording with 30, later 64 microelectrodes from monkey visual cortex (1979-1999) Neurologische Universitätsklinik, Freiburg,
AG Hirnforschung, Freiburg.
Recording with 64 chronically implanted microelectrodes from the mirror neurone area F5 in monkey ventral premotor cortex (2000-today; Dip. Neuroscienze, Università degli Studi, Parma)
Considerations, partly related to monkeys, how the phenomenal contents
of consciousness are related to neuronal activity (1998 until today).
Comments on my previous work:
The transition from physics to neuroscience was facilitated by a 2-year
stipend from Volkswagen Foundation (1972-73). My immediate interest was
to get new types of insight into cerebral activity
by using large numbers of electrodes. I wanted to be able to "orient
myself" within the neuronal activity alone, i.e. to know what is going
on without relying, at the
same time, on the knowledge about the environment of the animal. This
is in fact the way how the animal uses its brain.
The attempt was delayed by several years. Looking back, and including
the work of other scientists one can summarize that there has never
been any great breakthrough brought about by the use of many electrodes
although the required technologies soon became easily available. Still
today one cannot say that the desire to understand the neuronal
activity by itself (so to speak, from within the brain) is a major
branch of neuroscience, although it is a prerequisiste for neuronal
prosthesis programs. This may partly be impeded by the implicit, hidden
expectation that the "neuronal order" should correspond to the entities
as they appear on the phenomenal level of consciousness of the
experimenter. Thus, instead of a neuronal procedure of "eating soup
with a spoon", one may (falsely) expect, within the neuronal activity,
a manifestation of "the spoon" as an object or "stimulus", or a "hand
movement" as a motor event, which is independent of further procedural circumstances. With these thoughts in mind I shall contribute soon to an exploration of the prefrontal cortex of the monkey at Dip. Neuroscienze, Parma.
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6. Mode of work of the retired scientist.
A great problem of research organisation is how to carry out research
on an interesting topic if the risk of success is too high. It is well
known that the main body of the research
community, consisting of doctorands and post-docs, cannot take the risk
of total failure after several years of hard work. The only persons who
can actually carry out such work are the directors themselves if their
positions are secure, auxiliary personel not striving for a research
career, and retired researchers. The directors cannot delegate
high-risk research to the "common" researcher (except for some smaller
cases in which a "rescue program" is prepared from the outset for the
case of failure; see my previous work) . Usually, the more "successful"
a director is, the more doctorands and post-docs are associated to
him/her, with the consequence that barely any time is left to execute him/herself a
high-risk project. Unfortunately,
they must even encourage work for which the risk of success is not too
high. Yet, often they carry some unconventional ideas in their minds
for which they cannot see any way to get them realised. In addition, if
too many scientific prerequisites are lacking for such projects, there
is no way to
receive a supporting grant, so that the path via paid auxiliary
personel is blocked, too.
Thus, only retired scientists can offer a way out of this dilemma,
all the more so as the general life expectation has greatly increased
during the last decennies, while the age of retirement has remained
rather constant in many countries. to tackle such work, a director of a
large group, charged with lots of organisatorial tasks, has to wait
until he/she reaches retirement him/herself.
The fraction of retired researchers willing to follow such a path may
be small. Yet, it might be greater if the research institutions had
clear plans how to use the potential of the retirees, how to make use
of otherwise non-used material and rooms, and on the other hand, how to cope with clearly
esoteric projects, and with researchers becoming senile. It would also be desirable to
initiate a clearcut open competition between retired and younger
scientists, and to create prices or awards for contributions obtained
after retirement age. Certainly, to begin with, one would not consider
the question of how a retired scientist should be paid. "Nothing" would
be fine for at least some of them. Rather, "results per Euro of total
costs" should be taken into consideration. An advantage of "fundamental
research", as compared to other branches of human activity, is that no
retiree "steals the work" of a younger person. There is enough work for
While waiting for adequate organisatorial steps, the retired
researcher has to behave in similar ways as the members of medieval
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