5 - Unitary function and sense of ego
Brandão et al. (1993) have provided evidence that
the inferior colliculus is an alerting center and further
suggested it might play a role in general awareness
and maintaining the conscious state [1]. Researchers
three decades earlier had already proposed a unifying
role for functions within midbrain auditory structures.
Jane et al. (1965) placed lesions at different levels of
the auditory pathway in cats and found that the priority
response to auditory over visual stimuli was abolished
with lesions of the inferior colliculus or its connection
(the brachium) to higher brain centers [2]. But
bilateral lesions of the brachium of the inferior
colliculus produced marked behavioral changes. Cats
with lesions of the brachium resisted handling, did not
groom themselves, appeared dazed, and became
mostly mute.
Jane et al. concluded that severing the brachium
amounted to a functional disconnection of areas of the
forebrain much larger than the auditory cortex.
Perhaps these wider areas of the cortex could be the
areas that evolved along with elaboration of auditory
alerting in primates; perhaps they evolved as targets
of auditory connections. Perhaps cortical connections
of the auditory system provide a kind of "internet" of
the brain.
Inadequate sensory stimulation due to parental
neglect was once thought to be the cause of arrested
cognitive development and emotional disturbance in
disorders like autism. But physical disruption of
auditory signal transmission from brainstem to
forebrain would seem a more likely a cause of sensory
deprivation.
Sprague et al. (1961) also produced severe
behavioral changes in cats by severing the lateral
lemniscal tracts between the superior olive and inferior
colliculus [3]; they compared the altered behavior they
observed to that of autistic children, and compared
their findings with those of Klüver and Bucy (1939)
who obtained a similar alteration of behavior after
removing the temporal lobes of monkeys [4].
The similar behavioral findings of Sprague et al. and
Jane et al. (1965) suggest that disconnection of the
inferior colliculi from auditory input or from the auditory
receptive fields of the temporal lobes can lead to
disinterest at least in the acoustic environment.
Denny-Brown (1962) described profound losses of
awareness, responsiveness, and drive in monkeys
after ablation of the superior colliculi [5]. Denny-Brown
also removed the anterior portions of the inferior
colliculi in his experiments, and thus possibly their
connections with the superior colliculi. Denny-Brown
proposed that the superior colliculus might be the most
essential structure for unitary function of the brain,
and locus of the physiological “ego.”
Denny-Brown (1962) compared his experimental
observations to a clinical case, that of a teen-aged girl
who suffered damage to the midbrain tectum after
being thrown from a horse. She remained in a partial
state of coma until her death, not showing recognition
of her parents or other people. Denny-Brown pointed
out the susceptibility to damage of the brain structures
just forward of the tentorium, which separates the
cerebellum from the midbrain. The superior and
inferior colliculi form the midbrain tectum and are in
proximity to the posterior fossa structures that
sometimes appear damaged in MRI scans of
individuals with autism (see figure 9).
Brandão et al. (1993) have provided evidence that
the inferior colliculus is an alerting center and further
suggested it might play a role in general awareness
and maintaining the conscious state [1]. Researchers
three decades earlier had already proposed a unifying
role for functions within midbrain auditory structures.
Jane et al. (1965) placed lesions at different levels of
the auditory pathway in cats and found that the priority
response to auditory over visual stimuli was abolished
with lesions of the inferior colliculus or its connection
(the brachium) to higher brain centers [2]. But
bilateral lesions of the brachium of the inferior
colliculus produced marked behavioral changes. Cats
with lesions of the brachium resisted handling, did not
groom themselves, appeared dazed, and became
mostly mute.
Jane et al. concluded that severing the brachium
amounted to a functional disconnection of areas of the
forebrain much larger than the auditory cortex.
Perhaps these wider areas of the cortex could be the
areas that evolved along with elaboration of auditory
alerting in primates; perhaps they evolved as targets
of auditory connections. Perhaps cortical connections
of the auditory system provide a kind of "internet" of
the brain.
Inadequate sensory stimulation due to parental
neglect was once thought to be the cause of arrested
cognitive development and emotional disturbance in
disorders like autism. But physical disruption of
auditory signal transmission from brainstem to
forebrain would seem a more likely a cause of sensory
deprivation.
Sprague et al. (1961) also produced severe
behavioral changes in cats by severing the lateral
lemniscal tracts between the superior olive and inferior
colliculus [3]; they compared the altered behavior they
observed to that of autistic children, and compared
their findings with those of Klüver and Bucy (1939)
who obtained a similar alteration of behavior after
removing the temporal lobes of monkeys [4].
The similar behavioral findings of Sprague et al. and
Jane et al. (1965) suggest that disconnection of the
inferior colliculi from auditory input or from the auditory
receptive fields of the temporal lobes can lead to
disinterest at least in the acoustic environment.
Denny-Brown (1962) described profound losses of
awareness, responsiveness, and drive in monkeys
after ablation of the superior colliculi [5]. Denny-Brown
also removed the anterior portions of the inferior
colliculi in his experiments, and thus possibly their
connections with the superior colliculi. Denny-Brown
proposed that the superior colliculus might be the most
essential structure for unitary function of the brain,
and locus of the physiological “ego.”
Denny-Brown (1962) compared his experimental
observations to a clinical case, that of a teen-aged girl
who suffered damage to the midbrain tectum after
being thrown from a horse. She remained in a partial
state of coma until her death, not showing recognition
of her parents or other people. Denny-Brown pointed
out the susceptibility to damage of the brain structures
just forward of the tentorium, which separates the
cerebellum from the midbrain. The superior and
inferior colliculi form the midbrain tectum and are in
proximity to the posterior fossa structures that
sometimes appear damaged in MRI scans of
individuals with autism (see figure 9).
- Brandão ML et al. (1993)
Mechanisms of defense in
the inferior colliculus. - Jane JA et al. (1965) The
function of the tectum for
attention to auditory stimuli in
the cat. - Sprague JM et al. (1961)
Attentive, affective, and
adaptive behavior in the cat. - Klüver H, Bucy PC (1939)
Preliminary analysis of
functions of the temporal
lobes in monkeys. - Denny-Brown D (1962) The
midbrain and motor
integration.
- Brandão ML, Melo LL, Cardoso SH (1993) Mechanisms of defense in the inferior
colliculus. Behavioural Brain Research 58:49-55 - Jane JA, Masterton RB, Diamond IT (1965) The function of the tectum for attention to
auditory stimuli in the cat. Journal of Comparative Neurology 125:165-192. - Sprague JM, Chambers WW, Stellar, E (1961) Attentive, affective, and adaptive behavior
in the cat. Science 133:165-173. - Klüver H & Bucy PC (1939) Preliminary analysis of functions of the temporal lobes in
monkeys. Archives of Neurology and Psychiatry 42:979-1000. - Denny-Brown D (1962) The midbrain and motor integration. Proceedings of the Royal
Society of Medicine 55:527-538.
