Final answer:
Olfactory sensory signals do not pass through the thalamus before reaching the cortex; they are directly transmitted to the olfactory cortex. The thalamus is a relay station for all other sensory signals that it also partially processes.
Step-by-step explanation:
All sensory signals, except those from the olfactory system, are transmitted through the central nervous system and are routed to the thalamus, which then sends them to the appropriate region of the cortex for processing. The thalamus acts as a crucial relay station for sensory (as well as motor) signals and also processes the information to some extent, influencing the importance or attention given to sensory stimuli. However, olfactory signals bypass the thalamus and go directly to the olfactory cortex for processing.
For example, in the case of visual information, signals from the retina travel through the thalamus to the primary visual cortex in the occipital lobe. Here, basic visual processing begins, leading to complex shape recognition and binocular depth cues based on the overlapping field of view from both eyes.
In contrast, the olfactory system is unique as olfactory signals travel directly to the olfactory cortex without passing through the thalamus, making it the only sensory pathway that does not require a synaptic relay in the thalamus.