October 8, 2007 - Sources of reflex responses to auditory information
Coleman JR, Clerici WJ. Sources of projections to subdivisions of the inferior
colliculus in the rat. J Comp Neurol. 1987 Aug 8;262(2):215-26.
"The source of afferents to the inferior colliculus is considered
to be extensive, with particular involvement of structures
of the auditory pathway. Major input is derived from
the cochlear nuclear, superior olivary complex (except the
medial nucleus of the trapezoid body), nuclei of the lateral
lemniscus, auditory cortex, and other sectors of inferior
colliculus ... One subdivision, the external cortex, in addition to
receiving afferents from auditory structures, is also the
recipient of input derived from somatosensory structures
(Robards, '79; Aitkin et al., '81) ...
In the present study the source and nature of ascending
and descending afferents to the external cortex, dorsal cortex,
and central nucleus of the rat inferior colliculus are
examined. Microinjections of horseradish peroxidase are
used to examine the distribution of input to these subdivisions
from auditory and somatosensory structures and from
other sources ... The results show the
collicular subdivisions have distinct patterns of input that
provide substrates for functional specialization." [p 216]
External cortex (EC): "Significant sources of
retrogradely labelled cells from the EC injection are provided
by brainstem somatosensory nuclei (Fig. 1). Label is
observed in the cuneate and gracile nuclei and the spinal
trigeminal nucleus. Projections from these lemniscal nuclei
to the EC appear to be entirely contralateral (Table 1).
HRP-containing cells of the cuneate and gracile nuclei are
relatively small and mostly fusiform shaped. Additional
labelled cells are also found scattered in the neuropil near
the dorsal column nuclei. Other labelled neurons in the
brainstem are seen in the lateral nucleus of substantia
nigra, parabrachial region, deep superior colliculus, midbrain
central gray, and periventricular nucleus and surrounding
region of hypothalamus." [p 218]
Dorsal cortex (DC):
DC injection yields heavy labelling in area 41 of the ipsilateral
cortex (Fig. 3). ... a few labelled neurons are observed in the
lateral nucleus of the substantia nigra and midbrain central gray."
[p218]
Central nucleus (CN):
In contradistinction to the dorsal and external cortices,
the central nucleus receives heavy input from the cochlear
nuclei and superior olivary complex [p 219]
"The CN apparently receives few afferents
from the auditory cortex and none from the medial geniculate
body. However, the rat CN receives projections from
collicular subdivisions that are innervated by auditory cortex.
Therefore, activity of CN neurons may be indirectly
influenced by cortical neurons." [p 223]
From the discussion:
"Unlike other subdivisions of the inferior colliculus, the
EC receives ascending information from brainstem somatosensory
groups. The prime identified sources are the contralateral
cuneate and gracile nuclei, as well as the
contralateral spinal trigeminal nucleus." [p 223 ]
"this area may be involved in general sensory signalling, perhaps
for aspects of motor coordination." [p 224]
"Unlike the CN and EC, the DC receives very substantial
sets of afferents from the auditory cortex. The DC is clearly
the major target for descending auditory information to the
inferior colliculus." [p 224]
"the EC receives relatively fewer afferents from cortex. Instead,
EC input is more dependent on other colliculus subdivisions,
the somatosensory lemniscal system, and
additional brainstem nuclei." [p 224]
SUMMARY: "The CN is dominated by ascending afferents
from several brainstem auditory nuclei. The cells of
the CN are, consequently, considered the primary or core
pathway in the midbrain for analysis of auditory signals.
On the other hand, the EC, which receives only modest
input from the brainstem auditory nuclei, also derives afferents
from the somatosensory lemniscal system and other
brainstem nuclei not receiving primary auditory afferents.
The EC may be involved in multisensory processing of
information involved in reflex behavior or in descending
control mechanisms. By virtue of connections of the DC
with CN and other collicular subdivisions, and the extensive
input to it from auditory cortex, this collicular subdivision
may be involved in modulation of the ascending core
pathway." [p 225]
Citations:
- Aitkin, L.M., H. Dickhaus, W. Schult, and M. Zimmerman (1978) External nucleus
of inferior colliculus: Auditory and spinal somatosensory afferents and their
interactions. J. Neurophysiol. 41:837-847.
- Aitkin, L.M., C.E. Kenyon, and P. Philpott (1Y81) The represenlation of the
auditory and eomatosensory systems in tho external nucleus of the cat inferior
col1iculu.r. .b Comp. Neurol. 1962-40.
- RoBards, M.J. (1979) Somatic neurons in the brainstem and neocortex
projecting to the external nucleus of the inferior colliculus: An anatomical study
in the opossum. J. Comp. Neurol. 184:547-566.
October 13, 2007 - Abnormal eye movement and visual search in autism
Brenner LA, Turner KC, Muller RA. Eye movement and visual search: are there
elementary abnormalities in autism? J Autism Dev Disord. 2007 Aug;37(7):1289-309.
Response in progress: The oculomotor nuclei are among the brainstem nuclei of
high metabolic rate that are susceptible to impairment in alcoholism, causing
ophthalmoparesis. The same brainstem nuclei are affected by asphyxia at birth.
Respiratory depression at birth is associated with development of autism. Although
complications and failure to breathe right away at birth are usually attributed to
some hypothetical genetic problem of mother or child, the brain can still be assumed
to be affected the way it was in monkeys subjected to asphyxia at birth. In addition
to the oculomotor nuclei, the inferior colliculi in the midbrain auditory pathway are
most severely affected by asphyxia. Injury of the inferior colliculi is associated with
loss of the ability to comprehend speech in several case reports of people with no
preexisting language disorder.
The oculomotor problems of children with autism should be investigated as part of
the neurological impairment of brainstem nuclei of high metabolic rate, susceptible
to every etiological cause of autism.
--
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anatomy of visual search: regional segregations within the frontal eye fields and
effective connectivity of the superior colliculus. Neuroimage, 15(4), 970–982.
McPeek, R., & Keller, E. (2004). Deficits in saccade target selection after
inactivation of superior colliculus. Nature Neuroscience, 7(7), 757–763.
Schlagg-Rey, M., Schlag, J., & Dassonville, P. (1992). How the frontal eye field can
impose a saccade goal on superior colliculus neurons. Journal of Neurophysiology,
67(4), 1003–1005.
Torvik A. Brain lesions in alcoholics: neuropathological observations. Acta Med
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Cogan DG, Witt ED, Goldman-Rakic PS. Ocular signs in thiamine-deficient monkeys
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October 25, 2007 - Research on auditory anatomy and function
The view still prevails that children with autism hear well enough to learn to speak.
Recent research on auditory anatomy, physiology, and neurochemistry is providing
evidence of how impairment of the auditory system can disrupt connections to other
sensory systems, and prevent normal maturation of the cortical language areas.
Further, inhibitory neurotransmitters play an essential role in preventing sounds from
being transmitted to the cortex as a crescendo of intolerable noise. Children with
autism often cover their ears as if in distress in noisy environments. Conrad feared
going into a room with a telephone, and often became very upset with the ringing of
a telephone.
The literature on auditory function is often difficult to begin to understand. Perhaps
the answer is to encourage experts in this field to consider autistic children as
interesting examples of disordered auditory function. They might come up with
suggestions long before some of us even begin to fully comprehend their research
with echo-locating bats, etc. A few research papers of interest, and worthy of
detailed study include:
- Khalfa S, Bruneau N, Roge B, Georgieff N, Veuillet E, Adrien JL, Barthelemy C, Collet L.
Increased perception of loudness in autism. Hear Res. 2004 Dec;198(1-2):87-92.
- Rosenhall U, Nordin V, Sandstrom M, Ahlsen G, Gillberg C. Autism and hearing loss. J
Autism Dev Disord. 1999 Oct;29(5):349-57.
- Campbell LE, Hughes M, Budd TW, Cooper G, Fulham WR, Karayanidis F, Hanlon MC,
Stojanov W, Johnston P, Case V, Schall U. Primary and secondary neural networks of
auditory prepulse inhibition: a functional magnetic resonance imaging study of sensorimotor
gating of the human acoustic startle response. Eur J Neurosci. 2007 Oct;26(8):2327-33.
- Gillespie DC, Kim G, Kandler K. Inhibitory synapses in the developing auditory system are
glutamatergic. Nat Neurosci. 2005 Mar;8(3):332-8.
- Bauer EE, Klug A, Pollak GD. Features of contralaterally evoked inhibition in the inferior
colliculus. Hear Res. 2000 Mar;141(1-2):80-96.
- Coleman JR, Clerici WJ. Sources of projections to subdivisions of the inferior colliculus in
the rat. J Comp Neurol. 1987 Aug 8;262(2):215-26.
- Sparks DL.The neural encoding of the location of targets for saccadic eye movements. J Exp
Biol. 1989 Sep;146:195-207.
- Garcia Del Cano G, Gerrikagoitia I, Alonso-Cabria A, Martinez-Millan L. Organization and
origin of the connection from the inferior to the superior colliculi in the rat. J Comp Neurol.
2006 Dec 10;499(5):716-31.
- Coomes Peterson D, Schofield BR. Projections from auditory cortex contact ascending
pathways that originate in the superior olive and inferior colliculus. Hear Res. 2007 Oct;232
(1-2):67-77.
- Winer JA, Lee CC. The distributed auditory cortex. Hear Res. 2007 Jul;229(1-2):3-13.
- Darrow KN, Maison SF, Liberman MC. Cochlear efferent feedback balances interaural
sensitivity. Nat Neurosci. 2006 Dec;9(12):1474-6.
- Schofield BR, Coomes DL. Pathways from auditory cortex to the cochlear nucleus in guinea
pigs. Hear Res. 2006 Jun-Jul;216-217:81-9.
- Winer JA. Decoding the auditory corticofugal systems. Hear Res. 2006 Feb;212(1-2):1-8.
- Manley GA, Köppl C (1998). Phylogenetic development of the cochlea and its innervation.
Current Opinion In Neurobiology 8:468-474.
- Kungel M and Friauf E (1995). Somatostatin and leu-enkephalin in the rat auditory brainstem
during fetal and postnatal development. Anatomy and Embryology, 191, 425-443.
- Kungel M, Piechotta K, Rietzel HJ, Friauf E. Influence of the neuropeptide somatostatin on
the development of dendritic morphology: a cysteamine-depletion study in the rat auditory
brainstem. Brain Res Dev Brain Res. 1997 Jul 18;101(1-2):107-14.
In progress