A Discontinuous Tonotopic Organization in the Inferior Colliculus of the Rat

A Discontinuous Tonotopic Organization in the Inferior Colliculus of the Rat Malmierca Izquierdo Cristaudo Hernández Pérez-González Covey Oliver

Tag layer of the DHSS Meta-Tagging Project. The article text is reproduced from the staged copy named in sourceDesc and is not altered; the tags are held separately in standOff so that overlapping and nested spans are preserved.

A Discontinuous Tonotopic Organization in the Inferior Colliculus of the Rat 2008 Journal of Neuroscience 10.1523/jneurosci.0238-08.2008 Malmierca2008-a-discontinuous-tonotopic-organization-in-th Malmierca2008-a-discontinuous-tonotopic-organization-in-th.txt, the project's staged copy d5f7c4c2fcce057b29106c043ad9351a57bb08a9 not-redistributable neuroscience

the paper's own words

the tag layer; a sentence written by the tagger about the paper, always anchored to a quotation but not itself a quotation

0 spans located by searching the stored text for the quote's exact words, allowing any whitespace between them the fine-grained spatial progression of best frequency through the central nucleus of the IC Quotation withheld because this record is not cleared for redistribution. whether the tonotopic map in the IC is a continuous gradient or a stepwise one, and how it relates to the anatomical laminae Quotation withheld because this record is not cleared for redistribution. shows the tonotopic progression is stepwise rather than continuous, in both multiunit maps and the distribution of single-unit best frequencies, and matches the anatomical lamina thickness Quotation withheld because this record is not cleared for redistribution. existence Quotation withheld because this record is not cleared for redistribution. tonotopic organization in the inferior colliculus Quotation withheld because this record is not cleared for redistribution. electrophysiology electrophysiology Quotation withheld because this record is not cleared for redistribution. mechanisms best frequencies are laid out as partially overlapping bandpass filters spaced one third of an octave apart, so near threshold the filter centre frequencies win out over the overlap regions and the measured distribution comes out saw-toothed Quotation withheld because this record is not cleared for redistribution. mechanisms the discrete physiological frequency steps arise because the map is built from anatomically discrete fibrodendritic laminae, each lamina acting as one frequency-band module Quotation withheld because this record is not cleared for redistribution. best frequencies are modelled as partially overlapping bandpass filters spaced a third of an octave apart, so near threshold the filter centres are favoured and produce a saw-toothed distribution Quotation withheld because this record is not cleared for redistribution. the frequency step size matches the axonal lamina thickness, about 140-150 microns Quotation withheld because this record is not cleared for redistribution. two to three flat neurons side by side may form the functional unit of a low-frequency lamina Quotation withheld because this record is not cleared for redistribution. electrode penetrations were angled roughly orthogonal to the isofrequency laminae so the steps would be crossed rather than followed Quotation withheld because this record is not cleared for redistribution. step size differs across structures and species and correlates with dendritic field width Quotation withheld because this record is not cleared for redistribution. Laminar width measurements were not corrected for histological shrinkage. what this limits: every laminar width figure: MEASUREMENTS ARE PRESENTED WITHOUT CORRECTION FOR SHRINKAGE Quotation withheld because this record is not cleared for redistribution. The mapping of the finding onto critical bands rests on two unverified assumptions, since the number of critical bands in the rat is unknown. what this limits: the mapping onto critical bands: THE NUMBER OF CRITICAL BANDS IN THE RAT IS NOT KNOWN, and the estimate rests on two stated assumptions Quotation withheld because this record is not cleared for redistribution. Twelve penetrations gave no clear or incomplete tonotopic progression and were excluded from analysis. what this limits: the proportion of penetrations showing the organisation: IN 12 PENETRATIONS, NO CLEAR TONOTOPIC ORGANIZATION WAS FOUND ... OR THE TONOTOPIC PROGRESSION WAS INCOMPLETE Quotation withheld because this record is not cleared for redistribution. steps of 50 microns or less were required to see the organisation at all, so the result depends on sampling resolution what this limits: any comparison with the earlier mapping literature: ELECTRODE STEPS OF 50 um OR LESS WERE NECESSARY TO OBSERVE THE STEPWISE ORGANIZATION ... PREVIOUS STUDIES USED LARGER STEPS ... AND THUS ARE LIKELY TO HAVE SAMPLED ACROSS THE STEPWISE ORGANIZATION Quotation withheld because this record is not cleared for redistribution. most single units were collected in earlier studies with unrelated aims, in two laboratories with different equipment what this limits: the single-unit half of the evidence: THE SINGLE-UNIT DATA WERE COLLECTED IN PREVIOUS EXPERIMENTS WITH DIFFERENT AIMS UNRELATED TO TONOTOPIC ORGANIZATION Quotation withheld because this record is not cleared for redistribution. the two recording systems had different frequency ceilings, 25 kHz and 40 kHz, in a study about the distribution of best frequencies what this limits: the frequency range every distribution covers: THE HIGHEST FREQUENCY PRODUCED BY THIS SYSTEM WAS LIMITED TO 40 kHz Quotation withheld because this record is not cleared for redistribution. the number of critical bands in the rat is not known and is estimated from two stated assumptions what this limits: the same scope as limitations[1] - the critical-band count is an estimate from assumptions, not a measurement in this species Quotation withheld because this record is not cleared for redistribution. the cortical comparison rests on reanalysing a figure from another group's paper what this limits: the cortical comparison: WE ANALYZED THE BF OF 198 CORTICAL SINGLE UNITS FROM A PREVIOUS STUDY (DORON ET AL., 2002, THEIR FIG. 2) USING THE SAME APPROACH Quotation withheld because this record is not cleared for redistribution. the critical band, imported as the functional interpretation of an anatomical lamina, with the rat count estimated from basilar membrane length Quotation withheld because this record is not cleared for redistribution. the clinical motivation - midbrain implants in trials need to know the spectral layout they are stimulating Quotation withheld because this record is not cleared for redistribution. the acoustic output calibrated in situ at each ear with a quarter-inch condenser microphone and a spectrum analyser eliminates: a systematic level error at one ear - without in-situ calibration a stated decibel value is a property of the equipment rather than of the sound reaching the animal · outcome (stated by the tagger, no quotation): held Quotation withheld because this record is not cleared for redistribution. tonotopy here is DISCONTINUOUS by construction of the claim - a stepwise progression with a defined space of tissue per frequency band, not a smooth gradient Quotation withheld because this record is not cleared for redistribution. the continuous view is named as an ASSUMPTION of the field rather than as a finding, which is what makes the paper a critique Quotation withheld because this record is not cleared for redistribution. best frequency is defined as the frequency with the lowest threshold, and threshold as the lowest level eliciting a response - the step structure is a property of BF so defined Quotation withheld because this record is not cleared for redistribution. a lamina is simultaneously an anatomical object (axonal band, 140-150 microns) and a functional one (a frequency step) - the paper's claim is that they are the same thing Quotation withheld because this record is not cleared for redistribution. claim_type: critique a second reading DIFFERING from the recorded value. Recorded: existence — note: a second reading, verbatim-verified, disagreeing with the value on the record. Not applied - a person decides. Quotation withheld because this record is not cleared for redistribution. method: multiunit mapping in 25-50 micron steps, single-unit frequency response areas from two laboratories, and 3D reconstruction of anatomically labelled axonal laminae a second reading DIFFERING from the recorded value. Recorded: electrophysiology — note: a second reading, verbatim-verified, disagreeing with the value on the record. Not applied - a person decides. Quotation withheld because this record is not cleared for redistribution. phenomenon: tonotopy as a discontinuous, laminar organisation a second reading DIFFERING from the recorded value. Recorded: tonotopic organization in the inferior colliculus — note: a second reading, verbatim-verified, disagreeing with the value on the record. Not applied - a person decides. Quotation withheld because this record is not cleared for redistribution. replicates → Schreiner and Langner, 1997 (stepwise tonotopy in cat CNIC) Quotation withheld because this record is not cleared for redistribution. contradicts → Rose et al., 1966; Clopton and Winfield, 1973; Merzenich and Reid, 1974 Quotation withheld because this record is not cleared for redistribution. extends → Doron et al., 2002 (rat primary auditory cortex single units) Quotation withheld because this record is not cleared for redistribution. contradicts → the general view that CNIC tonotopy is a continuous frequency gradient Quotation withheld because this record is not cleared for redistribution. explains-away → the earlier mapping studies that reported continuity, on the grounds that they sampled too coarsely to resolve the steps Quotation withheld because this record is not cleared for redistribution. confirms → Schreiner and Langner's stepwise organisation in cat, at a different step size Quotation withheld because this record is not cleared for redistribution. extends → Doron et al.'s cortical single-unit data, reanalysed here and found to show the same periodicity Quotation withheld because this record is not cleared for redistribution. supports → the proposal that critical band filters originate at the midbrain Quotation withheld because this record is not cleared for redistribution. EVIDENCE CORRECTED (RE-GROUNDED) · stepwise —contrasted-with→ continuous stepwise continuous EVIDENCE CORRECTED: RE-GROUNDED. The old span argued against a general view without naming either term. This sentence names both and states the contrast in eight words - 'Some appear to be CONTINUOUS, WHEREAS others are STEPWISE' - which is the cleanest contrast span merged tonight. — strength of the relation: 1 · note: the paper's whole claim; and note that the corpus holds both descriptions of IC tonotopy as findings, from this paper and from the studies it refutes Quotation withheld because this record is not cleared for redistribution. best frequency —operationalised-as→ frequency response areas best frequency frequency response areas strength of the relation: 1 Audit 2026-09-28: DOUBTFUL - read against its full span and kept, but best frequency is DEFINED as the frequency with the lowest threshold; 'frequency response areas' is not in the span. Quotation withheld because this record is not cleared for redistribution. tonotopic organization —operationalised-as→ multiunit tonotopic organization multiunit strength of the relation: 0.9 · note: RE-GROUNDS another row of this record: the old span named NEITHER endpoint. Audit 2026-09-28: DOUBTFUL - read against its span and kept, but the span reports stepwise tonotopy in multiunit recordings; operationalised-as is loose. Quotation withheld because this record is not cleared for redistribution. Mann-Whitney U test Mann-Whitney U test Quotation withheld because this record is not cleared for redistribution. linear regression linear regression Quotation withheld because this record is not cleared for redistribution. correlation coefficient correlation coefficient Quotation withheld because this record is not cleared for redistribution. mean and standard deviation mean and standard deviation Quotation withheld because this record is not cleared for redistribution. histogram (binned frequency distribution) histogram (binned frequency distribution) Quotation withheld because this record is not cleared for redistribution. smoothing (fast Fourier transform) smoothing (fast Fourier transform) Quotation withheld because this record is not cleared for redistribution. curve fitting (sigmoidal function) curve fitting (sigmoidal function) Quotation withheld because this record is not cleared for redistribution. logarithmic histogram of best frequencies with peak picking logarithmic histogram of best frequencies with peak picking Quotation withheld because this record is not cleared for redistribution. repeated measurement of the same unit over time repeated measurement of the same unit over time Quotation withheld because this record is not cleared for redistribution. Sampling best frequency every 25-50 micrometres revealed a stair-step rather than smooth progression in every penetration through the central nucleus of the inferior colliculus. Quotation withheld because this record is not cleared for redistribution. Best frequency stayed within 0.1 octaves for about 151 micrometres of electrode travel and then jumped by about a third of an octave. Quotation withheld because this record is not cleared for redistribution. Best frequencies of 604 independently recorded single units were not uniformly distributed but clustered into 16 peaks spaced about a third of an octave apart. Quotation withheld because this record is not cleared for redistribution. Step thickness and step size were statistically indistinguishable between low-frequency and high-frequency regions, so laminae are similar throughout the central nucleus. Quotation withheld because this record is not cleared for redistribution. The thinnest anatomically labelled axonal laminae, once corrected for histological shrinkage, are the same size as the physiological frequency steps, tying the stair-step map to the fibrodendritic laminae. Quotation withheld because this record is not cleared for redistribution. Reanalysed cortical single units showed a similar multipeaked best-frequency distribution, with peaks about 0.31 octaves apart. Quotation withheld because this record is not cleared for redistribution. Taken together the multiunit and single-unit data contradict the standard assumption that the inferior colliculus contains a continuous low-to-high frequency gradient. Quotation withheld because this record is not cleared for redistribution. multiunit maps show a distinct stepwise progression of best frequency Quotation withheld because this record is not cleared for redistribution. single-unit best frequencies cluster at intervals of about one third of an octave Quotation withheld because this record is not cleared for redistribution. the two lines of evidence argue against a continuous gradient Quotation withheld because this record is not cleared for redistribution. earlier studies reporting continuity used larger electrode steps and would have sampled across the structure Quotation withheld because this record is not cleared for redistribution. best frequency of a unit stays constant over 23 to 80 minutes, varying 50 times less than the step size Quotation withheld because this record is not cleared for redistribution. axonal lamina thickness and frequency step size are both about 140-150 microns Quotation withheld because this record is not cleared for redistribution. reanalysing another group's cortical single units shows the same periodicity, r = 0.998 Quotation withheld because this record is not cleared for redistribution. the data suggest 8-12 laminae of 0.29-0.36 octaves each, similar to the 0.333-0.375-octave critical bands suggested for the mouse Quotation withheld because this record is not cleared for redistribution. midbrain filters appear roughly twice as broad as peripheral auditory filters Quotation withheld because this record is not cleared for redistribution. tonotopic organization tonotopic organization Quotation withheld because this record is not cleared for redistribution. width of the plexus width of the plexus Quotation withheld because this record is not cleared for redistribution. bandpass filters bandpass filters Quotation withheld because this record is not cleared for redistribution. threshold threshold Quotation withheld because this record is not cleared for redistribution. BF BF Quotation withheld because this record is not cleared for redistribution. BF BF Quotation withheld because this record is not cleared for redistribution. cross-sectional diameter cross-sectional diameter Quotation withheld because this record is not cleared for redistribution. body temperature body temperature Quotation withheld because this record is not cleared for redistribution. best frequency best frequency Quotation withheld because this record is not cleared for redistribution. depth along the electrode track depth along the electrode track Quotation withheld because this record is not cleared for redistribution. Electrode steps Electrode steps Quotation withheld because this record is not cleared for redistribution. 137 — pigmented rats from which extracellular activity was recorded Quotation withheld because this record is not cleared for redistribution. 604 — single-unit frequency response areas obtained, from 125 rats Quotation withheld because this record is not cleared for redistribution. 0.34 ± 0.11 octaves — mean jump in best frequency at each step of the multiunit staircase (460 steps) Quotation withheld because this record is not cleared for redistribution. 14 ± 3.7 — average number of frequency steps per electrode track Quotation withheld because this record is not cleared for redistribution. r = 0.99855 — correlation between the 12 matched best-frequency peaks of the single-unit and multiunit datasets Quotation withheld because this record is not cleared for redistribution. 104 ± 21 μm — mean cross-sectional diameter of the seven thinnest anatomically labelled axonal laminae Quotation withheld because this record is not cleared for redistribution. 0.006 ± 0.0002 octaves — drift of best frequency at a fixed recording site over 23-80 minutes, about 50 times smaller than a staircase step Quotation withheld because this record is not cleared for redistribution. 142 ± 69 μm — mean thickness of a best-frequency step in low-frequency regions (below 4 kHz) Quotation withheld because this record is not cleared for redistribution. 2180 ± 460 μm — average length of the recorded dorsoventral electrode tracks Quotation withheld because this record is not cleared for redistribution. ∼8–12 — estimated number of critical bands in the rat, based on an 8 mm basilar membrane Quotation withheld because this record is not cleared for redistribution. about 0.29 octaves per step in rat, against 0.278 in cat and about 1 octave in rabbit MGV — step size across structures and species value source note: THE VALUE DRAWS ON THE PAPER BEYOND THIS QUOTE: part of it is printed elsewhere in the paper, not in this quote ('or rat [∼ 0.29 octaves (present data)]…'). Quotation withheld because this record is not cleared for redistribution. 140-150 microns — both the axonal lamina thickness and the spatial period of the frequency steps Quotation withheld because this record is not cleared for redistribution. 0.006 octaves mean change, variance 0.0002, 50 times smaller than the 0.34 octave jumps — stability of best frequency over 23 to 80 minutes Quotation withheld because this record is not cleared for redistribution. 8-12 critical bands from an 8 mm basilar membrane, and 8-12 laminae observed — two independent estimates agreeing Quotation withheld because this record is not cleared for redistribution. 604 frequency response areas from 125 rats, 400 of them from earlier studies — the single-unit dataset and its provenance Quotation withheld because this record is not cleared for redistribution. 137 rats of both sexes — the full sample Quotation withheld because this record is not cleared for redistribution. 25 kHz in one system and 40 kHz in the other — the differing stimulus ceilings of the two laboratories contributing single units value source note: THE VALUE DRAWS ON THE PAPER BEYOND THIS QUOTE: part of it is printed elsewhere in the paper, not in this quote ('frequency produced by this system was limited to 25 kHz.'). Quotation withheld because this record is not cleared for redistribution. r = 0.99841 — correlation between IC and cortical best-frequency distributions Quotation withheld because this record is not cleared for redistribution.

The full text of this article is not redistributable, so it is not included here. The evidence sentences are withheld with it; the tag layer and its grounding status remain. The article itself is at https://doi.org/10.1523/jneurosci.0238-08.2008.