Plasticity and the Mystacial Vibrissae of Rodents

The thalamic reticular nucleus (Rt) is strategically positioned to integrate descending and ascending signals in the control of sensorimotor and other thalamocortical activity. Its prominent role in the generation of sleep spindles notwithstanding, relatively little is known of Rt function in regulating interactions with the sensory environment. We recorded and compared the responses of individual Rt and thalamocortical neurons in the ventroposterior medial (VPm) nucleus of the rat to controlled deflections of mystacial vibrissae. Transient Rt responses to the onset (on) and offset (off) of vibrissa deflection are larger and longer in duration than those of VPm and of all other populations studied in the whisker/barrel pathway. Magnitudes of on and off responses in Rt were negatively correlated with immediately preceding activities, suggesting a contribution of low-threshold T-type Ca2+ channels. Rt neurons also respond with high tonic firing rates during sustained vibrissa deflections. By comparison, VPm neurons are less likely to respond tonically and are more likely to exhibit tonic suppression. Rt and VPm populations are similar to each other, however, in that they retain properties of directional sensitivity established in primary afferent neurons. In both populations neurons are selective for deflection angle and exhibit directional consistency, responding best to a particular direction of movement regardless of the starting position of the vibrissal hair. These findings suggest a role for Rt in the processing of detailed sensory information. Temporally, Rt may function to limit the duration of stimulus-evoked VPm responses and to focus them on rapid vibrissa perturbations. Moreover, by regulating the baseline activity of VPm neurons, Rt may indirectly enhance the response selectivity of layer IV barrel neurons to synchronous VPm firing.

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Rats’ responsiveness to tactile changes encountered in the dark, and the role of mystacial vibrissae

Behavioural Brain Research ◽

10.1016/j.bbr.2007.02.023 ◽

2007 ◽

Vol 179 (2) ◽

pp. 273-280 ◽

Cited By ~ 4

Author(s):

Robert N. Hughes

Keyword(s):

Mystacial Vibrissae

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Use of Rhodamine B as a systemic bait marker for feral cats (Felis catus)

Wildlife Research ◽

10.1071/wr98041 ◽

1999 ◽

Vol 26 (3) ◽

pp. 281 ◽

Cited By ~ 14

Author(s):

P. Fisher ◽

D. Algar ◽

J. Sinagra

Keyword(s):

Rhodamine B ◽

Uv Light ◽

Field Studies ◽

Ambient Light ◽

Captive Population ◽

Feral Cats ◽

Hair Samples ◽

Mystacial Vibrissae ◽

Single Blind ◽

Single Blind Trial

A number of cats in a captive population were fed 50 mg of Rhodamine B in non-toxic kangaroo meat baits. Samples of whiskers (mystacial vibrissae) taken 10 days later were examined for fluorescent marking. Examination of hairs for marking was carried out by means of a ‘single blind’ trial, with the investigator having no prior knowledge of which of 36 cats had received the dye. All of the cats that had ingested baits containing the dye were marked. Examining hair samples under ambient light or under a hand-held ultraviolet (UV) light without magnification was not as reliable as examining hair samples under a fluorescence microscope. These results indicate that Rhodamine B acts as a reliable systemic marker of bait consumption in feral cats and has potential application in field studies to assess bait uptake by feral cats.

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The early development of mystacial vibrissae in the mouse

Development ◽

10.1242/dev.83.1.137 ◽

1984 ◽

Vol 83 (1) ◽

pp. 137-156

Author(s):

Joan T. Wrenn ◽

Norman K. Wessells

Keyword(s):

Flat Surface ◽

Temporal Correlation ◽

Cell Types ◽

Nerve Branch ◽

Complex Process ◽

Initial Generation ◽

Mystacial Vibrissae ◽

Vertical Row ◽

Early Mouse ◽

A Site

The initial generation of the pattern of mystacial vibrissae (whiskers) in the mouse is described. The maxillary process is present in 10-day embryos but has a relatively flat surface. Beginning at approximately 11·5 days, the first sign of vibrissal development is the formation of ridges and grooves on the maxillary and lateral nasal processes. The first vibrissal rudiment to form subsequently appears posterior to the most ventral groove on the maxillary process. It is the most ventral whisker of the posterior, vertical row. The next few rudiments appear: (1) dorsal to the first, also in the vertical row; and (2) anterior to the first, on the ventral-most ridge and in the groove beneath it. Formation of vibrissal rudiments continues in a dorsal and anterior progression usually by an apparent partitioning of the ridges into vibrissal units. The hypothesis that this patterning of mystacial vibrissae might be determined by the pattern of innervation in the early mouse snout was investigated. Nerve trunks and branches are present in the maxillary process well before any sign of vibrissal formation. Because innervation is so widespread there appears to be no immediate temporal correlation between the outgrowth of a nerve branch to a site and the generation of a vibrissa there. Furthermore, at the time just prior to the formation of the first follicle rudiment, there is little or no nerve branching to the presumptive site of that first follicle while branches are found more dorsally where vibrissae will not form until later. Thus, a one-to-one spatial correlation between nerve and follicle sites also appears to be lacking. The developmental changes in ultrastructure within the neurites of the trunks and branches as well as the apparent rearrangements of the nerve trunks suggest that early innervation of the snout is a labile phenomenon and that the vibrissal pattern begins to be established before the neural pattern is completely developed. The results indicate that vibrissal pattern formation is likely to be a complex process relying on the interplay of the cells and tissues involved, rather than on unidirectional instructions from neurons to other cell types.

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Receptive-field properties of rat ventral posterior medial neurons before and after selective kainic acid lesions of the trigeminal brain stem complex

Journal of Neurophysiology ◽

10.1152/jn.1987.57.5.1577 ◽

1987 ◽

Vol 57 (5) ◽

pp. 1577-1600 ◽

Cited By ~ 72

Author(s):

R. W. Rhoades ◽

G. R. Belford ◽

H. P. Killackey

Keyword(s):

Receptive Field ◽

Kainic Acid ◽

Appreciable Effect ◽

Guard Hair ◽

Peripheral Stimulation ◽

Receptive Field Properties ◽

Before And After ◽

Mystacial Vibrissae ◽

Nucleus Principalis ◽

Intact Rats

Single neurons were recorded from the ventral posteromedial thalamic nucleus (VPM) of urethan-anesthetized rats. Six of these animals were intact, 28 sustained kainic acid (KA) lesions of trigeminal nucleus principalis (PrV), and 9 received similar lesions of trigeminal subnucleus interpolaris (SpVi). Four animals sustained PrV lesions that were followed, at an interval of 1-3 mo, by KA injections into SpVi. Special attention was paid to the receptive-field characteristics of neurons that were sensitive to deflection of the mystacial vibrissae. In normal animals, we recorded a total of 167 VPM neurons, 85% (n = 142) of which were vibrissa sensitive. The remaining VPM cells were excited by either guard hair deflection (8.4%), indentation of the skin (0.6%), or deflection of either vibrissae or guard hairs (1.8%). Seven cells (4.2%) were unresponsive. The topography of the trigeminal representation in VPM was similar to that reported previously by Waite (59). Vibrissa-sensitive neurons in intact rats generally gave rapidly adapting responses (84.5%), and only 16.2% were directionally selective. The vast majority (80.3%) of the vibrissa-sensitive cells were activated by deflection of only one whisker (1.2 +/- 0.5, mean +/- SD); none were excited by deflection of more than four vibrissae. Injections of KA into SpVi of otherwise intact rats (n = 9) had no appreciable effect on the receptive-field characteristics of vibrissa-sensitive VPM neurons. Injections of KA into PrV markedly altered the receptive-field properties of VPM cells. Recordings were made from 45 VPM neurons over a period extending from 0 to 10 h after KA injections into PrV in five rats. Of these cells, 4.4% were excited by vibrissa deflection and the remainder were unresponsive. Additional recordings from SpVi and the superior colliculus of these same animals indicated that the neurotoxin probably did not damage interpolaris neurons or their axons. Recordings were made from 394 VPM cells in 22 rats that survived 1-6 days after KA lesions of PrV. These experiments demonstrated an increase in the number of thalamic cells that were responsive to peripheral stimulation over this period. By 6 days after the lesion (4 animals), 52.8% of the 73 VPM neurons we recorded were excited by somatosensory stimuli. Of these, 89.5% were activated by deflection of one or more mystacial vibrissae. The average number of whiskers that excited a given VPM cell in these rats was 6.3 +/- 2.0 (SD). Recordings were made from VPM in five rats that survived 30-90 days after KA injections in PrV.(ABSTRACT TRUNCATED AT 400 WORDS)

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Active vibrissal sensing in rodents and marsupials

Philosophical Transactions of the Royal Society B Biological Sciences ◽

10.1098/rstb.2011.0156 ◽

2011 ◽

Vol 366 (1581) ◽

pp. 3037-3048 ◽

Cited By ~ 74

Author(s):

Ben Mitchinson ◽

Robyn A. Grant ◽

Kendra Arkley ◽

Vladan Rankov ◽

Igor Perkon ◽

...

Keyword(s):

Fourier Analysis ◽

Active Control ◽

Fundamental Frequency ◽

Horizontal Plane ◽

Second Harmonic ◽

Early Stage ◽

Monodelphis Domestica ◽

Head Turning ◽

Previous Evidence ◽

Mystacial Vibrissae

In rats, the long facial whiskers (mystacial macrovibrissae) are repetitively and rapidly swept back and forth during exploration in a behaviour known as ‘whisking’. In this paper, we summarize previous evidence from rats, and present new data for rat, mouse and the marsupial grey short-tailed opossum ( Monodelphis domestica ) showing that whisking in all three species is actively controlled both with respect to movement of the animal's body and relative to environmental structure. Using automatic whisker tracking, and Fourier analysis, we first show that the whisking motion of the mystacial vibrissae, in the horizontal plane, can be approximated as a blend of two sinusoids at the fundamental frequency (mean 8.5, 11.3 and 7.3 Hz in rat, mouse and opossum, respectively) and its second harmonic. The oscillation at the second harmonic is particularly strong in mouse (around 22 Hz) consistent with previous reports of fast whisking in that species. In all three species, we found evidence of asymmetric whisking during head turning and following unilateral object contacts consistent with active control of whisker movement. We propose that the presence of active vibrissal touch in both rodents and marsupials suggests that this behavioural capacity emerged at an early stage in the evolution of therian mammals.

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Decreased Heterogeneity of Capillary Plasma Flow in the Rat Whisker-Barrel Cortex during Functional Hyperemia

Journal of Cerebral Blood Flow & Metabolism ◽

10.1097/00004647-199611000-00026 ◽

1996 ◽

Vol 16 (6) ◽

pp. 1300-1306 ◽

Cited By ~ 34

Author(s):

Johannes Vogel ◽

Wolfgang Kuschinsky

Keyword(s):

Evans Blue ◽

Barrel Cortex ◽

Stimulation Frequency ◽

Blue Dye ◽

Functional Hyperemia ◽

Transit Times ◽

Mystacial Vibrissae ◽

The Right ◽

The Brain ◽

Experimental Group

The pattern of capillary plasma perfusion was investigated in the rat brain during functional activation. Functional hyperemia was induced in the left whisker-barrel cortex by deflection of the right mystacial vibrissae for 2 min at frequencies of 1–7 Hz. Rats were decapitated under anesthesia 3 s after i.v. bolus injection of Evans blue dye. The steep increase of the arterial dye concentration ensures that divergent capillary plasma transit times result in unequal intracapillary dye concentrations. Plasma perfusion heterogeneity was determined from the coefficient of variation (CV) of Evans blue concentrations measured in numerous single capillaries of the whisker-barrel cortex. Functional hyperemia was quantified from measurements of CBF using the [14C]-iodoantipyrine technique in a second experimental group. CBF in the left whisker-barrel cortex increased with the stimulation frequency and was maximal at 5 Hz compared to the right side. Conversely, plasma perfusion heterogeneity decreased with stimulation frequency in a reciprocal way, being minimal at 5 Hz. Results indicate a decrease in the microcirculatory flow heterogeneity during functional hyperemia in the brain.

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